Announcement

Collapse
No announcement yet.

US FluView - Weekly Surveillance Flu report 2021/2022 season - for trend analysis

Collapse
This is a sticky topic.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • US FluView - Weekly Surveillance Flu report 2021/2022 season - for trend analysis

    Previous thread FluView thread here. Sorry for the spotty thread, but there was very little flu reported for 2020/2021 season.


    Weekly U.S. Influenza Surveillance Report





    Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

    2020-2021 Influenza Season for Week 39, ending October 2, 2021

    All data are preliminary and may change as more reports are received.

    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

    Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.
    U.S. Virologic Surveillance:

    Clinical Laboratories


    Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.



    View Chart Data | View Full ScreenPublic Health Laboratories


    Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.



    View Chart Data | View Full Screen


    Additional information about medically attended visits for ILI for current and past seasons:
    Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
    Outpatient Illness Surveillance


    Please note, the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness (ILI), not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. In addition, health care-seeking behaviors have changed dramatically during the COVID-19 pandemic. Many people are accessing the health care system in alternative settings, which may or may not be captured as a part of ILINet. Therefore, ILI data, including ILI activity levels, should be interpreted with caution. It is particularly important at this time to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
    ILINet


    Nationwide during week 39, 1.9% of patient visits reported through ILINet were due to ILI. The percentage of patient visits for ILI remains below the baseline of 2.6% nationally. All ten regions are below their region-specific baselines.

    Influenza virus circulation remains low; therefore, increases in ILI activity are likely due to increased circulation of other respiratory viruses.



    View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


    About 65% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

    The percentages of visits for ILI reported in ILINet are decreasing among all age groups (0-4 years, 5-24 years, 25-49 years, 50-64 years, and 65+ years).



    View Chart Data | View Full ScreenILI Activity Map


    Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
    Week 39
    (Week ending
    Oct. 2, 2021)
    Week 38
    (Week ending
    Sep. 25, 2021)
    Week 39
    (Week ending
    Oct. 2, 2021)
    Week 38
    (Week ending
    Sep. 25, 2021)
    Very High 0 0 0 0
    High 0 1 7 7
    Moderate 1 0 16 32
    Low 10 10 74 71
    Minimal 42 44 474 495
    Insufficient Data 2 0 358 324


    *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

    Additional information about medically attended visits for ILI for current and past seasons:
    Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
    Influenza-Associated Hospitalizations:


    The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. As in previous seasons, patients admitted for laboratory-confirmed influenza-related hospitalization after April 30, 2021, will not be included in FluSurv-NET. Data on patients admitted through April 30, 2021, will continue to be updated as additional information is received.

    Additional hospitalization surveillance information for current and past seasons and additional age groups:
    Surveillance Methods | FluView Interactive: Rates by Age or Patient Characteristics
    National Center for Health Statistics (NCHS) Mortality Surveillance


    Based on NCHS mortality surveillance data available on October 7, 2021, 18.7% of the deaths that occurred during the week ending October 2, 2021 (week 39), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.7% for this week. Among the 3,296 PIC deaths reported for this week, 2,607 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and four listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



    View Chart Dataexcel icon | View Full Screen

    Additional pneumonia and influenza mortality surveillance information for current and past seasons:
    Surveillance Methods | FluView Interactive
    Influenza-Associated Pediatric Mortality


    No influenza-associated pediatric deaths were reported to CDC during week 39.

    One influenza-associated pediatric death occurring during the 2020-2021 season has been reported to CDC.


    View Full Screen

    Additional pediatric mortality surveillance information for current and past seasons:
    Surveillance Methods | FluView Interactive


    Additional National and International Influenza Surveillance Information


    FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

    National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

    U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
    Additional influenza surveillance information from participating WHO member nations is available through
    FluNetexternal icon and the Global Epidemiology Reports.external icon

    WHO Collaborating Centers for Influenza:
    Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

    Europe:
    The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

    Public Health Agency of Canada:
    The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

    Public Health England:
    The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

    Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

    Page last reviewed: October 8, 2021, 11:00 AM

    https://www.cdc.gov/flu/weekly/index.htm

  • #2

    Weekly U.S. Influenza Surveillance Report




    Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

    Key Updates for Week 40, ending October 9, 2021

    Seasonal influenza activity in the United States remains low.
    Viruses


    Clinical Lab0.1%


    positive for influenza

    Public Health Lab
    Few specimens have tested positive.

    Virus Characterization
    Influenza virus characterization information will be reported later this season.
    Illness

    Outpatient Illness: ILINet1.9%


    of visits to a health care provider for ILI
    (below baseline)


    Outpatient Illness: ILINet Activity Map


    This week, 1 jurisdiction experienced high or very high activity and 1 jurisdiction experienced moderate activity.

    Long Term Care Facilities0.1%


    Of facilities reported
    ≥ 1 influenza-positive tests
    among residents

    Severe Disease


    FluSurv-NET
    Hospitalization rates will be updated starting later this season.

    HHS Protect Hospitalizations276


    patients admitted to hospitals with flu

    NCHS Mortality18.0%


    of deaths attributed to pneumonia, influenza, or COVID-19 (above threshold)

    Pediatric Deaths0


    deaths occurring this season

    All data are preliminary and may change as more reports are received.

    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

    Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

    Key Points
    • An annual flu vaccine is the best way to protect against flu and its potentially serious complications.
    • CDC recommends everyone 6 months or older get a flu vaccine by the end of October.
    • There also are flu antiviral drugs that can be used to treat flu illness.
    U.S. Virologic Surveillance:

    Clinical Laboratories


    The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

    No. of specimens tested 41,539 28,951
    No. of positive specimens (%) 48 (0.1%) 42 (0.1%)
    Positive specimens by type
    Influenza A 24 (50.0%) 24 (57.1%)
    Influenza B 24 (50.0%) 18 (42.9%)



    View Chart Data | View Full ScreenPublic Health Laboratories


    The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
    No. of specimens tested 17,400 14,615
    No. of positive specimens 5 13
    Positive specimens by type/subtype
    Influenza A 3 (60.0%) 8 (61.5%)
    (H1N1)pdm09 0 1 (50.0%)
    H3N2 2 (100%) 1 (50.0%)
    Subtyping not performed 1 6
    Influenza B 2 (40.0%) 5 (38.5%)
    Yamagata lineage 1 (100%) 0
    Victoria lineage 0 1 (100%)
    Lineage not performed 1 4

    View Chart Data | View Full Screen

    Additional virologic surveillance information for current and past seasons:
    Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
    Influenza Virus Characterization


    CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

    Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
    Outpatient Illness Surveillance


    The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

    Effective October 3, 2021, the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.” This change was made to improve the consistency with which the definition is applied across reporting sites
    ILINet


    Nationwide during week 40, 1.9% of patient visits reported through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) were due to influenza-like illness (ILI). This percentage is below the national baseline of 2.5%. Three regions (Region 2, Region 3, and Region 7) are at their region-specific baseline while the remaining regions are below their baselines. Overall, influenza virus circulation remains low; therefore, increases in ILI activity are likely due to increased circulation of other respiratory viruses.



    View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


    More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

    The percentages of visits for ILI reported in ILINet in week 40 remained stable compared to week 39 for all age groups (0–4 years, 5–24 years, 25–49 years, 50–64 years, and 65+ years) and is showing a decreasing trend over at least the past four weeks for all age groups.



    View Chart Data | View Full ScreenILI Activity Map


    Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
    Week 40
    (Week ending
    Oct. 9, 2021)
    Week 39
    (Week ending
    Oct. 2, 2021)
    Week 40
    (Week ending
    Oct. 9, 2021)
    Week 39
    (Week ending
    Oct. 2, 2021)
    Very High 1 0 1 0
    High 0 0 3 7
    Moderate 1 1 22 18
    Low 5 9 91 77
    Minimal 48 43 503 485
    Insufficient Data 0 2 309 342



    *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

    Additional information about medically attended visits for ILI for current and past seasons:
    Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
    Long-term Care Facility (LTCF) Surveillance


    LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents the NHSN Long-term Care Facility Component. During week 40, 18 (0.13%) of 14,297 reporting LTCFs reported at least one laboratory-confirmed influenza test among their residents.



    View Chart Dataexcel icon | View Full Screen

    Additional information about long-term care facility surveillance:
    Surveillance Methods | Additional Dataexternal icon
    Hospitalization Surveillance

    FluSurv-NET


    The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

    Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
    Surveillance Methods | FluView Interactive
    HHS-Protect Hospitalization Surveillance


    Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 40, 276 patients with laboratory-confirmed influenza were admitted to the hospital.



    View Chart Dataexcel icon | View Full Screen

    Additional HHS Protect hospitalization surveillance information:
    Surveillance Methods | Additional Dataexternal icon
    Mortality Surveillance

    National Center for Health Statistics (NCHS) Mortality Surveillance


    Based on NCHS mortality surveillance data available on October 14, 2021, 18.0% of the deaths that occurred during the week ending October 9, 2021 (week 40), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.7% for this week. Among the 3,102 PIC deaths reported for this week, 2,430 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and two listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



    View Chart Dataexcel icon | View Full Screen

    Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
    Surveillance Methods | FluView Interactive
    Influenza-Associated Pediatric Mortality


    No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


    View Full Screen

    Additional pediatric mortality surveillance information for current and past seasons:
    Surveillance Methods | FluView Interactive


    Additional National and International Influenza Surveillance Information


    FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

    National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

    U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
    Additional influenza surveillance information from participating WHO member nations is available through
    FluNetexternal icon and the Global Epidemiology Reports.external icon

    WHO Collaborating Centers for Influenza:
    Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

    Europe:
    The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

    Public Health Agency of Canada:
    The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

    Public Health England:
    The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

    Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

    Page last reviewed: October 15, 2021, 11:00 AM

    https://www.cdc.gov/flu/weekly/index.htm

    Comment


    • #3

      Weekly U.S. Influenza Surveillance Report




      Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

      Key Updates for Week 41, ending October 16, 2021

      Seasonal influenza activity in the United States remains low.
      Viruses


      Clinical Lab0.1%


      positive for influenza

      Public Health Lab
      Few specimens have tested positive.

      Virus Characterization
      Influenza virus characterization information will be reported later this season.
      Illness

      Outpatient Illness: ILINet1.8%


      of visits to a health care provider for ILI
      (below baseline)


      Outpatient Illness: ILINet Activity Map


      This week, 2 jurisdictions experienced moderate activity and no jurisdictions experienced high or very high activity.

      Long-term Care Facilities0.1%


      of facilities reported
      ≥ 1 influenza-positive tests
      among residents

      Severe Disease


      FluSurv-NET
      Hospitalization rates will be updated starting later this season.

      HHS Protect Hospitalizations248


      patients admitted to hospitals with flu

      NCHS Mortality17.5%


      of deaths attributed to pneumonia, influenza, or COVID-19 (above threshold)

      Pediatric Deaths0


      influenza-associated deaths occurring this
      season


      All data are preliminary and may change as more reports are received.

      A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

      Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

      Key Points
      • An annual flu vaccine is the best way to protect against flu and its potentially serious complications.
      • CDC recommends everyone 6 months or older get a flu vaccine by the end of October.
      • There also are flu antiviral drugs that can be used to treat flu illness.
      U.S. Virologic Surveillance

      Clinical Laboratories


      The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

      No. of specimens tested 28,629 69,314
      No. of positive specimens (%) 36 (0.1%) 97 (0.1%)
      Positive specimens by type
      Influenza A 17 (47.2%) 51 (52.6%)
      Influenza B 19 (52.8%) 46 (47.4%)



      View Chart Data | View Full ScreenPublic Health Laboratories


      The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
      No. of specimens tested 15,209 30,809
      No. of positive specimens 10 24
      Positive specimens by type/subtype
      Influenza A 5 (50.0%) 13 (54.2%)
      (H1N1)pdm09 0 1 (11.1%)
      H3N2 4 (100%) 8 (88.9%)
      Subtyping not performed 1 4
      Influenza B 5 (40.0%) 11 (45.8%)
      Yamagata lineage 0 1 (33.3%)
      Victoria lineage 1 (100%) 2 (66.7%)
      Lineage not performed 4 8

      View Chart Data | View Full Screen

      Additional virologic surveillance information for current and past seasons:
      Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
      Novel Influenza A Virus


      Two human infections with novel influenza A viruses were reported. One infection with an influenza A(H1N1) variant (A(H1N1)v) virus was reported by North Dakota that occurred during the 2020-21 influenza season and one infection with an influenza (A(H3N2)v) virus was reported by Ohio that occurred during the 2021-22 influenza season. Both patients are <18 years of age, were not hospitalized, and have recovered or are recovering from their illness. One of the patients had close contact with swine prior to illness onset. The other patient had no known swine contact or attendance at agricultural exhibits where swine were present; it is possible that limited human-to-human transmission occurred. No ongoing human-to-human transmission has been identified associated with either patient.

      When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus”. Most human infections with variant influenza viruses occur following close proximity to swine, but human-to-human transmission can occur. It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.

      During the 2021-22 influenza season, one human infection with novel influenza A virus has been reported in the United States: H3N2v (OH). During the 2020-21 influenza season, 11 human infections with a novel influenza A virus were reported in the United States, including two H3N2v (IA, WI), three H1N2v (IA, OH (2)), and six H1N1v (IA, NC, ND, WI (3)) virus infections.

      Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be more fully understood and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza virus infection in humans, and strategies to interact safely with swine can be found at www.cdc.gov/flu/swineflu/index.htm. Additional information regarding human infections with novel influenza A viruses can be found at http://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.
      Influenza Virus Characterization


      CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

      Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
      Outpatient Illness Surveillance


      The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

      Effective October 3, 2021, the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.” This change was made to improve the consistency with which the definition is applied across reporting sites
      ILINet


      Nationwide during week 41, 1.8% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.5%. One region (Region 7) is at their region-specific baseline while the remaining regions are below their baselines. Overall, influenza virus circulation remains low; therefore, increases in ILI activity are likely due to increased circulation of other respiratory viruses.



      * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


      View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


      More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

      The percentages of visits for ILI reported in ILINet in week 41 decreased or remained stable compared to week 40 for all age groups (0–4 years, 5–24 years, 25–49 years, 50–64 years, and 65+ years) and is showing a decreasing or stabilizing trend over at least the past four weeks for all age groups.



      * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

      View Chart Data | View Full Screen
      ILI Activity Map


      Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
      Week 41
      (Week ending
      Oct. 16, 2021)
      Week 40
      (Week ending
      Oct. 9, 2021)
      Week 41
      (Week ending
      Oct. 16, 2021)
      Week 40
      (Week ending
      Oct. 9, 2021)
      Very High 0 0 0 1
      High 0 0 4 3
      Moderate 2 2 18 23
      Low 6 5 77 90
      Minimal 47 48 538 525
      Insufficient Data 0 0 292 287



      *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

      Additional information about medically attended visits for ILI for current and past seasons:
      Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
      Long-term Care Facility (LTCF) Surveillance


      LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents the NHSN Long-term Care Facility Component. During week 41, 19 (0.1%) of 14,271 reporting LTCFs reported at least one influenza positive test among their residents.



      View Chart Dataexcel icon | View Full Screen

      Additional information about long-term care facility surveillance:
      Surveillance Methods | Additional Dataexternal icon
      Hospitalization Surveillance

      FluSurv-NET


      The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

      Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
      Surveillance Methods | FluView Interactive
      HHS-Protect Hospitalization Surveillance


      Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 41, 248 patients with laboratory-confirmed influenza were admitted to the hospital.



      View Chart Dataexcel icon | View Full Screen

      Additional HHS Protect hospitalization surveillance information:
      Surveillance Methods | Additional Dataexternal icon
      Mortality Surveillance

      National Center for Health Statistics (NCHS) Mortality Surveillance


      Based on NCHS mortality surveillance data available on October 21, 2021, 17.5% of the deaths that occurred during the week ending October 16, 2021 (week 41), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.8% for this week. Among the 2,885 PIC deaths reported for this week, 2,208 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and none listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



      View Chart Dataexcel icon | View Full Screen

      Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
      Surveillance Methods | FluView Interactive
      Influenza-Associated Pediatric Mortality


      No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


      View Full Screen

      Additional pediatric mortality surveillance information for current and past seasons:
      Surveillance Methods | FluView Interactive


      Additional National and International Influenza Surveillance Information


      FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

      National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

      U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
      Additional influenza surveillance information from participating WHO member nations is available through
      FluNetexternal icon and the Global Epidemiology Reports.external icon

      WHO Collaborating Centers for Influenza:
      Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

      Europe:
      The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

      Public Health Agency of Canada:
      The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

      Public Health England:
      The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

      Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

      A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

      Page last reviewed: October 22, 2021, 11:00 AM

      https://www.cdc.gov/flu/weekly/index.htm

      Comment


      • #4

        Weekly U.S. Influenza Surveillance Report


        Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

        Key Updates for Week 42, ending October 23, 2021

        Seasonal influenza activity in the United States remains low.
        Viruses


        Clinical Lab0.1%


        positive for influenza
        this week


        Public Health Lab
        Few specimens have tested positive.

        Virus Characterization
        Influenza virus characterization information will be reported later this season.
        Illness

        Outpatient Illness: ILINet1.8%


        of visits to a health care provider for ILI this week
        (below baseline)


        Outpatient Illness: ILINet Activity Map


        This week, 1 jurisdiction experienced moderate activity and no jurisdictions experienced high or very high activity.

        Long-term Care Facilities0.2%


        of facilities reported
        ≥ 1 influenza-positive tests
        among residents this week

        Severe Disease


        FluSurv-NET
        Hospitalization rates will be updated starting later this season.

        HHS Protect Hospitalizations288


        patients admitted to hospitals with flu
        this week


        NCHS Mortality16.5%


        of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

        Pediatric Deaths0


        influenza-associated deaths occurring
        this season


        All data are preliminary and may change as more reports are received.

        A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

        Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

        Key Points
        • An annual flu vaccine is the best way to protect against flu and its potentially serious complications.
        • CDC recommends everyone 6 months and older get a flu vaccine.
        • There also are flu antiviral drugs that can be used to treat flu illness.
        U.S. Virologic Surveillance

        Clinical Laboratories


        The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

        No. of specimens tested 30,338 111,986
        No. of positive specimens (%) 26 (0.1%) 134 (0.1%)
        Positive specimens by type
        Influenza A 10 (38.5%) 63 (47.0%)
        Influenza B 16 (61.5%) 71 (53.0%)



        View Chart Data | View Full ScreenPublic Health Laboratories


        The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
        No. of specimens tested 20,253 51,864
        No. of positive specimens 8 39
        Positive specimens by type/subtype
        Influenza A 7 (87.5%) 22 (56.4%)
        (H1N1)pdm09 0 1 (7.7%)
        H3N2 1 (100%) 11 (84.6%)
        H3N2v 0 1 (7.7%)
        Subtyping not performed 6 9
        Influenza B 1 (12.5%) 17 (43.6%)
        Yamagata lineage 0 2 (28.6 %)
        Victoria lineage 0 5 (71.4%)
        Lineage not performed 1 10

        View Chart Data | View Full Screen

        Additional virologic surveillance information for current and past seasons:
        Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
        Influenza Virus Characterization


        CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

        Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
        Outpatient Illness Surveillance


        The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

        Effective October 3, 2021, the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.” This change was made to improve the consistency with which the definition is applied across reporting sites
        ILINet


        Nationwide during week 42, 1.8% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.5%. All regions are below their baselines. Overall, influenza virus circulation remains low; therefore, any increase in ILI activity is likely due to increased circulation of other respiratory viruses.



        * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


        View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


        More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

        The percentages of visits for ILI reported in ILINet in week 42 remained stable compared to week 41 for all age groups and is showing a decreasing or stable trend during at least the past four weeks for all age groups (0–4 years, 5–24 years, 25–49 years, 50–64 years, and 65+ years).



        * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

        View Chart Data | View Full Screen
        ILI Activity Map


        Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
        Week 42
        (Week ending
        Oct. 23, 2021)
        Week 41
        (Week ending
        Oct. 16, 2021)
        Week 42
        (Week ending
        Oct. 23, 2021)
        Week 41
        (Week ending
        Oct. 16, 2021)
        Very High 0 0 0 0
        High 0 0 5 4
        Moderate 1 2 15 17
        Low 3 6 69 79
        Minimal 50 47 534 553
        Insufficient Data 1 0 306 276



        *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

        Additional information about medically attended visits for ILI for current and past seasons:
        Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
        Long-term Care Facility (LTCF) Surveillance


        LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents the NHSN Long-term Care Facility Component. During week 42, 26 (0.2%) of 14,302 reporting LTCFs reported at least one influenza positive test among their residents.



        View Chart Dataexcel icon | View Full Screen

        Additional information about long-term care facility surveillance:
        Surveillance Methods | Additional Dataexternal icon
        Hospitalization Surveillance

        FluSurv-NET


        The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

        Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
        Surveillance Methods | FluView Interactive
        HHS-Protect Hospitalization Surveillance


        Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 42, 288 patients with laboratory-confirmed influenza were admitted to the hospital.



        View Chart Dataexcel icon | View Full Screen

        Additional HHS Protect hospitalization surveillance information:
        Surveillance Methods | Additional Dataexternal icon
        Mortality Surveillance

        National Center for Health Statistics (NCHS) Mortality Surveillance


        Based on NCHS mortality surveillance data available on October 28, 2021, 16.5% of the deaths that occurred during the week ending October 23, 2021 (week 42), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.9% for this week. Among the 2,994 PIC deaths reported for this week, 2,188 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and four listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



        View Chart Dataexcel icon | View Full Screen

        Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
        Surveillance Methods | FluView Interactive
        Influenza-Associated Pediatric Mortality


        No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


        View Full Screen

        Additional pediatric mortality surveillance information for current and past seasons:
        Surveillance Methods | FluView Interactive


        Additional National and International Influenza Surveillance Information


        FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

        National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

        U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
        Additional influenza surveillance information from participating WHO member nations is available through
        FluNetexternal icon and the Global Epidemiology Reports.external icon

        WHO Collaborating Centers for Influenza:
        Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

        Europe:
        The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

        Public Health Agency of Canada:
        The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

        Public Health England:
        The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

        Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

        A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

        Page last reviewed: October 29, 2021, 11:00 AM


        https://www.cdc.gov/flu/weekly/index.htm

        Comment


        • #5
          bump this

          Comment


          • #6

            Weekly U.S. Influenza Surveillance Report


            Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

            Key Updates for Week 43, ending October 30, 2021

            Seasonal influenza activity in the United States remains low, but the number of influenza virus detections reported by public health laboratories has increased in recent weeks.
            Viruses


            Clinical Lab0.2%


            positive for influenza
            this week


            Public Health Lab
            A small but increasing
            number of specimens have
            tested positive.


            Virus Characterization
            Influenza virus characterization information will be reported later this season.
            Illness

            Outpatient Illness: ILINet1.9%


            of visits to a health care provider for ILI this week
            (below baseline)


            Outpatient Illness: ILINet Activity Map


            This week, 2 jurisdictions experienced moderate activity and no jurisdictions experienced high or very high activity.

            Long-term Care Facilities0.2%


            of facilities reported
            ≥ 1 influenza-positive test
            among residents this week

            Severe Disease


            FluSurv-NET
            Hospitalization rates will be updated starting later this season.

            HHS Protect Hospitalizations282


            patients admitted to hospitals with influenza
            this week


            NCHS Mortality15.6%


            of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

            Pediatric Deaths0


            influenza-associated deaths occurring
            this season


            All data are preliminary and may change as more reports are received.

            A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

            Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

            Key Points
            • While influenza activity is low nationally, the number of influenza viruses detected by public health labs has increased in recent weeks.
            • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
            • There also are flu antiviral drugs that can be used to treat flu illness.
            U.S. Virologic Surveillance

            Clinical Laboratories


            The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

            No. of specimens tested 32,943 156,261
            No. of positive specimens (%) 52 (0.2%) 218 (0.1%)
            Positive specimens by type
            Influenza A 34 (65.4%) 113 (51.8%)
            Influenza B 18 (34.6%) 105 (48.2%)



            View Chart Data | View Full ScreenPublic Health Laboratories


            The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
            No. of specimens tested 21,720 76,169
            No. of positive specimens 35 89
            Positive specimens by type/subtype
            Influenza A 32 (91.4%) 64 (71.9%)
            (H1N1)pdm09 0 1 (2.0%)
            H3N2 25 (100%) 49 (96.1%)
            H3N2v 0 1 (2.0%)
            Subtyping not performed 7 13
            Influenza B 3 (8.6%) 25 (28.1%)
            Yamagata lineage 0 2 (18.2 %)
            Victoria lineage 2 (100%) 9 (81.8%)
            Lineage not performed 1 14

            View Chart Data | View Full Screen

            Additional virologic surveillance information for current and past seasons:
            Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
            Novel Influenza A Virus


            Three human infections with novel influenza A viruses that occurred during the 2020-21 influenza season were reported. One human infection with novel influenza A(H1N2) variant (A(H1N2)v) was reported by Indiana and two human infections with influenza A(H1N1)v were reported by Iowa. All three patients were adults ≥ 18 years of age, were not hospitalized, and have recovered from their illness. All three patients had attended an agricultural event where swine were present and/or visited a farm where swine were present. No ongoing human-to-human transmission was identified associated with any of these patients.

            During the 2020-21 influenza season, 14 human infections with a novel influenza A viruses were reported in the United States, including two H3N2v (IA, WI), four H1N2v (IA, IN, OH (2)), and eight H1N1v (IA (3), NC, ND, WI (3)) virus infections. During the 2021-22 influenza season, one human infection with a novel influenza A virus has been reported in the United States: H3N2v (OH).

            When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus”. Most human infections with variant influenza viruses occur following close proximity to swine, but human-to-human transmission can occur. It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person. Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be more fully understood and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza virus infection in humans, and strategies to interact safely with swine can be found at www.cdc.gov/flu/swineflu/index.htm. Additional information regarding human infections with novel influenza A viruses can be found at http://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.
            Influenza Virus Characterization


            CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

            Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
            Outpatient Illness Surveillance


            The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
            ILINet


            Nationwide during week 43, 1.9% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.5%. All regions are below their baselines. Overall, influenza virus circulation remains low; therefore, any increase in ILI activity is likely due to increased circulation of other respiratory viruses.



            * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


            View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


            More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

            The percentages of visits for ILI reported in ILINet in week 43 remained stable compared to week 42 for all age groups and is showing a stable trend during at least the past four weeks for all age groups (0–4 years, 5–24 years, 25–49 years, 50–64 years, and 65+ years).



            * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

            View Chart Data | View Full Screen
            ILI Activity Map


            Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
            Week 43
            (Week ending
            Oct. 30, 2021)
            Week 42
            (Week ending
            Oct. 23, 2021)
            Week 43
            (Week ending
            Oct. 30, 2021)
            Week 42
            (Week ending
            Oct. 23, 2021)
            Very High 0 0 0 0
            High 0 0 7 5
            Moderate 2 1 18 15
            Low 4 3 78 70
            Minimal 49 51 541 547
            Insufficient Data 0 0 285 292



            *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

            Additional information about medically attended visits for ILI for current and past seasons:
            Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
            Long-term Care Facility (LTCF) Surveillance


            LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 43, 27 (0.2%) of 14,216 reporting LTCFs reported at least one influenza positive test among their residents.



            View Chart Dataexcel icon | View Full Screen

            Additional information about long-term care facility surveillance:
            Surveillance Methods | Additional Dataexternal icon
            Hospitalization Surveillance

            FluSurv-NET


            The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

            Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
            Surveillance Methods | FluView Interactive
            HHS-Protect Hospitalization Surveillance


            Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 43, 282 patients with laboratory-confirmed influenza were admitted to the hospital.



            View Chart Dataexcel icon | View Full Screen

            Additional HHS Protect hospitalization surveillance information:
            Surveillance Methods | Additional Dataexternal icon
            Mortality Surveillance

            National Center for Health Statistics (NCHS) Mortality Surveillance


            Based on NCHS mortality surveillance data available on November 4, 2021, 15.6% of the deaths that occurred during the week ending October 30, 2021 (week 43), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.0% for this week. Among the 3,086 PIC deaths reported for this week, 2,224 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and one listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



            View Chart Dataexcel icon | View Full Screen

            Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
            Surveillance Methods | FluView Interactive
            Influenza-Associated Pediatric Mortality


            No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


            View Full Screen

            Additional pediatric mortality surveillance information for current and past seasons:
            Surveillance Methods | FluView Interactive


            Additional National and International Influenza Surveillance Information


            FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

            National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

            U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
            Additional influenza surveillance information from participating WHO member nations is available through
            FluNetexternal icon and the Global Epidemiology Reports.external icon

            WHO Collaborating Centers for Influenza:
            Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

            Europe:
            The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

            Public Health Agency of Canada:
            The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

            Public Health England:
            The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

            Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

            A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

            Page last reviewed: November 5, 2021, 11:00 AM
            Content source: Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)


            https://www.cdc.gov/flu/weekly/index.htm

            Comment


            • #7

              Weekly U.S. Influenza Surveillance Report


              Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

              Key Updates for Week 44, ending November 6, 2021

              Seasonal influenza activity in the United States remains low, but the number of influenza virus detections reported by public health laboratories has increased in recent weeks.
              Viruses


              Clinical Lab0.3%


              positive for influenza
              this week


              Public Health Lab
              A small but increasing
              number of specimens have
              tested positive.


              Virus Characterization
              Influenza virus characterization information will be reported later this season.
              Illness

              Outpatient Illness: ILINet2.1%


              of visits to a health care provider for ILI this week
              (below baseline)


              Outpatient Illness: ILINet Activity Map


              This week, 1 jurisdiction experienced moderate activity and 1 jurisdiction experienced high or very high activity.

              Long-term Care Facilities0.1%


              of facilities reported
              ≥ 1 influenza-positive test
              among residents this week

              Severe Disease


              FluSurv-NET
              Hospitalization rates will be updated starting later this season.

              HHS Protect Hospitalizations295


              patients admitted to hospitals with influenza
              this week


              NCHS Mortality14.1%


              of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

              Pediatric Deaths0


              influenza-associated deaths occurring
              this season


              All data are preliminary and may change as more reports are received.

              A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

              Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

              Key Points
              • While influenza activity is low nationally, the number of influenza viruses detected by public health labs has increased in recent weeks.
              • The majority of viruses detected are A(H3N2). More than 90% are among children and young adults aged 5-24 years.
              • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
              • As of October 29, 2021, 158.7M doses of flu vaccine have been distributed in the US.
              • Flu vaccines are available at many different locations including pharmacies and health departments.
              • Visit www.vaccines.gov to find a flu vaccine near you. There also are flu antiviral drugs that can be used to treat flu illness.
              U.S. Virologic Surveillance

              Clinical Laboratories


              The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

              No. of specimens tested 34,828 201,409
              No. of positive specimens (%) 101 (0.3%) 320 (0.2%)
              Positive specimens by type
              Influenza A 78 (77.2%) 188 (58.8%)
              Influenza B 23 (22.8%) 132 (41.3%)



              View Chart Data | View Full ScreenPublic Health Laboratories


              The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
              No. of specimens tested 21,450 107,933
              No. of positive specimens 110 429
              Positive specimens by type/subtype
              Influenza A 107 (97.3%) 401 (93.5%)
              (H1N1)pdm09 0 1 (0.3%)
              H3N2 102 (100%) 383 (99.5%)
              H3N2v 0 1 (0.3%)
              Subtyping not performed 5 16
              Influenza B 3 (2.7%) 28 (6.5%)
              Yamagata lineage 0 2 (15.4 %)
              Victoria lineage 3 (100%) 11 (84.6%)
              Lineage not performed 0 15

              Overall influenza activity is still low; however, an increasing number of an influenza A(H3N2) viruses have been reported by public health laboratories in the most recent weeks. During the most recent three weeks, influenza A(H3N2) viruses have been reported by public health laboratories in seven of the 10 HHS regions (Regions 1, 3, 4, 5, 7, 8, and 9). Among 102 A(H3N2) viruses reported for week 44, 68 (66.7%) were reported by Michigan. The majority of influenza positives reported from Michigan can be linked to a single outbreak among young adults. Additionally, during week 44, a large backfill of data from previous weeks was received from Region 3. For regional and state level data about circulating influenza viruses, please visit FluView Interactive.





              View Chart Data | View Full Screen

              Additional virologic surveillance information for current and past seasons:
              Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
              Influenza Virus Characterization


              CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

              Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
              Outpatient Illness Surveillance


              The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
              ILINet


              Nationwide during week 44, 2.1% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.5%. Region 7 is above their region-specific baseline, and all other regions are below their baselines. Multiple respiratory viruses are co-circulating; therefore, the relative contribution of influenza virus infection to ILI varies by location.



              * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


              View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


              More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

              The percentages of visits for ILI reported in ILINet in week 44 increased for two age groups (0–4 years, 5–24 years) and remained stable for three age groups (25–49 years, 50–64 years, and 65+ years) compared to week 43. All age groups are showing a small increase or stable trend over the past four weeks.



              * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

              View Chart Data | View Full Screen
              ILI Activity Map


              Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
              Week 44
              (Week ending
              Nov. 6, 2021)
              Week 43
              (Week ending
              Oct. 30, 2021)
              Week 44
              (Week ending
              Nov. 6, 2021)
              Week 43
              (Week ending
              Oct. 30, 2021)
              Very High 0 0 2 0
              High 1 0 9 9
              Moderate 1 3 28 18
              Low 10 2 81 79
              Minimal 40 50 517 552
              Insufficient Data 3 0 292 271



              *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

              Additional information about medically attended visits for ILI for current and past seasons:
              Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
              Long-term Care Facility (LTCF) Surveillance


              LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 44, 18 (0.1%) of 14,228 reporting LTCFs reported at least one influenza positive test among their residents.



              View Chart Dataexcel icon | View Full Screen

              Additional information about long-term care facility surveillance:
              Surveillance Methods | Additional Dataexternal icon
              Hospitalization Surveillance

              FluSurv-NET


              The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

              Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
              Surveillance Methods | FluView Interactive
              HHS-Protect Hospitalization Surveillance


              Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 44, 295 patients with laboratory-confirmed influenza were admitted to the hospital.



              View Chart Dataexcel icon | View Full Screen

              Additional HHS Protect hospitalization surveillance information:
              Surveillance Methods | Additional Dataexternal icon
              Mortality Surveillance

              National Center for Health Statistics (NCHS) Mortality Surveillance


              Based on NCHS mortality surveillance data available on November 10, 2021, 14.1% of the deaths that occurred during the week ending November 6, 2021 (week 44), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.1% for this week. Among the 2,230 PIC deaths reported for this week, 1,551 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and none listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



              View Chart Dataexcel icon | View Full Screen

              Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
              Surveillance Methods | FluView Interactive
              Influenza-Associated Pediatric Mortality


              No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


              View Full Screen

              Additional pediatric mortality surveillance information for current and past seasons:
              Surveillance Methods | FluView Interactive


              Additional National and International Influenza Surveillance Information


              FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

              National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

              U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
              Additional influenza surveillance information from participating WHO member nations is available through
              FluNetexternal icon and the Global Epidemiology Reports.external icon

              WHO Collaborating Centers for Influenza:
              Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

              Europe:
              The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

              Public Health Agency of Canada:
              The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

              Public Health England:
              The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

              Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

              A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

              Page last reviewed: November 5, 2021, 11:00 AM
              Content source: Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)

              Comment


              • #8

                Weekly U.S. Influenza Surveillance Report


                Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

                Key Updates for Week 45, ending November 13, 2021

                Seasonal influenza activity in the United States remains low, but the number of influenza virus detections reported by clinical and public health laboratories and the percent of patient visits for influenza-like illness has increased in recent weeks.
                Viruses


                Clinical Lab0.7%


                positive for influenza
                this week


                Public Health Lab
                A small but increasing
                number of specimens have
                tested positive.


                Virus Characterization
                Influenza virus characterization information will be reported later this season.
                Illness

                Outpatient Illness: ILINet2.1%


                of visits to a health care provider for ILI this week
                (below baseline)


                Outpatient Illness: ILINet Activity Map


                This week, 1 jurisdiction experienced moderate activity and 1 jurisdiction experienced high or very high activity.

                Long-term Care Facilities0.2%


                of facilities reported
                ≥ 1 influenza-positive test
                among residents this week

                Severe Disease


                FluSurv-NET
                Hospitalization rates will be updated starting later this season.

                HHS Protect Hospitalizations332


                patients admitted to hospitals with influenza
                this week


                NCHS Mortality14.4%


                of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

                Pediatric Deaths0


                influenza-associated deaths occurring
                this season


                All data are preliminary and may change as more reports are received.

                A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

                Key Points
                • While influenza activity is low nationally, the number of influenza viruses detected by clinical and public health labs has increased in recent weeks.
                • The majority of viruses detected are A(H3N2). More than 90% are among children and young adults aged 5-24 years.
                • Although the percent of outpatient visits for ILI remains below baseline, the percent of ILI visits have been slowly increasing in recent weeks.
                • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
                • As of November 5, 2021, 162.5M doses of flu vaccine have been distributed in the US.
                • Flu vaccines are available at many different locations including pharmacies and health departments. Visit www.vaccines.gov to find a flu vaccine near you.
                • There also are flu antiviral drugs that can be used to treat flu illness.
                U.S. Virologic Surveillance

                Clinical Laboratories


                The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

                No. of specimens tested 38,685 265,492
                No. of positive specimens (%) 257 (0.7%) 702 (0.3%)
                Positive specimens by type
                Influenza A 228 (88.7%) 522 (74.4%)
                Influenza B 29 (11.3%) 180 (25.6%)



                View Chart Data | View Full ScreenPublic Health Laboratories


                The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.

                Overall influenza activity is still low; however, an increasing number of influenza positive tests have been reported by clinical and public health laboratories during recent weeks; the majority of which are influenza A(H3N2). During the most recent three weeks, influenza A(H3N2) viruses have been reported by public health laboratories in eight of the 10 HHS regions (Regions 1, 2, 3, 4, 5, 7, 8, and 9). So far during the 2021-22 season 448 (91.1%) of the 492 A(H3N2) viruses with known age were reported among children and young adults aged 5-24 years. For regional and state level data about circulating influenza viruses, please visit FluView Interactive.
                No. of specimens tested 20,249 129,357
                No. of positive specimens 140 621
                Positive specimens by type/subtype
                Influenza A 136 (97.1%) 587 (94.5%)
                (H1N1)pdm09 0 1 (0.2%)
                H3N2 75 (100%) 503 (99.6%)
                H3N2v 0 1 (0.2%)
                Subtyping not performed 61 82
                Influenza B 4 (2.9%) 34 (5.5%)
                Yamagata lineage 0 3 (18.8%)
                Victoria lineage 1 (100%) 13 (81.3%)
                Lineage not performed 3 18



                View Chart Data | View Full Screen

                Additional virologic surveillance information for current and past seasons:
                Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
                Influenza Virus Characterization


                CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

                Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
                Outpatient Illness Surveillance


                The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [(ILI) fever plus cough or sore throat], not laboratory-confirmed influenza, and will capture visits due to other respiratory pathogens, such as SARS-CoV-2, that present with similar symptoms. Due to the COVID-19 pandemic, health care-seeking behaviors have changed and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, COVID-19, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
                ILINet


                Nationwide during week 45, 2.1% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.5%. All regions are below their baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI can vary by location.



                * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


                View Chart Data (current season only) | View Full ScreenILI Visits by Age Group


                More than 70% of ILINet participants provide both the number of patient visits for ILI and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for ILI by age group.

                The percentages of visits for ILI reported in ILINet in week 45 increased for two age groups (0–4 years, 5–24 years) and remained stable for three age groups (25–49 years, 50–64 years, and 65+ years) compared to week 44.



                * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

                View Chart Data | View Full Screen
                ILI Activity Map


                Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
                Week 45
                (Week ending
                Nov. 13, 2021)
                Week 44
                (Week ending
                Nov. 6, 2021)
                Week 45
                (Week ending
                Nov. 13, 2021)
                Week 44
                (Week ending
                Nov. 6, 2021)
                Very High 0 0 2 2
                High 1 1 15 11
                Moderate 1 1 38 29
                Low 8 7 92 80
                Minimal 44 45 493 533
                Insufficient Data 1 1 289 274



                *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

                Additional information about medically attended visits for ILI for current and past seasons:
                Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
                Long-term Care Facility (LTCF) Surveillance


                LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 45, 24 (0.2%) of 14,223 reporting LTCFs reported at least one influenza positive test among their residents.



                View Chart Dataexcel icon | View Full Screen

                Additional information about long-term care facility surveillance:
                Surveillance Methods | Additional Dataexternal icon
                Hospitalization Surveillance

                FluSurv-NET


                The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

                Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
                Surveillance Methods | FluView Interactive
                HHS-Protect Hospitalization Surveillance


                Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 45, 332 patients with laboratory-confirmed influenza were admitted to the hospital.



                View Chart Dataexcel icon | View Full Screen

                Additional HHS Protect hospitalization surveillance information:
                Surveillance Methods | Additional Dataexternal icon
                Mortality Surveillance

                National Center for Health Statistics (NCHS) Mortality Surveillance


                Based on NCHS mortality surveillance data available on November 18, 2021, 14.4% of the deaths that occurred during the week ending November 13, 2021 (week 45), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.2% for this week. Among the 3,046 PIC deaths reported for this week, 2,175 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and four listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



                View Chart Dataexcel icon | View Full Screen

                Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
                Surveillance Methods | FluView Interactive
                Influenza-Associated Pediatric Mortality


                No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


                View Full Screen

                Additional pediatric mortality surveillance information for current and past seasons:
                Surveillance Methods | FluView Interactive


                Additional National and International Influenza Surveillance Information


                FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

                National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

                U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
                Additional influenza surveillance information from participating WHO member nations is available through
                FluNetexternal icon and the Global Epidemiology Reports.external icon

                WHO Collaborating Centers for Influenza:
                Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

                Europe:
                The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

                Public Health Agency of Canada:
                The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

                Public Health England:
                The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

                Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

                A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                Page last reviewed: November 19, 2021, 11:00 AM

                https://www.cdc.gov/flu/weekly/

                Comment


                • #9
                  bump this

                  Comment


                  • #10

                    Weekly U.S. Influenza Surveillance Report


                    Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

                    Key Updates for Week 47, ending November 27, 2021

                    Seasonal influenza activity in the United States remains low, but in recent weeks, the number of influenza virus detections reported by clinical and public health laboratories has increased, and the percent of outpatient visits for respiratory illness has trended upward.
                    Viruses


                    Clinical Lab1.5%


                    positive for influenza
                    this week


                    Public Health Lab
                    A small but increasing
                    number of specimens have
                    tested positive. The majority of viruses are influenza A(H3N2).


                    Virus Characterization
                    Influenza virus characterization information will be reported later this season.
                    Illness

                    Outpatient Respiratory Illness2.4%


                    of visits to a health care provider for respiratory illness this week
                    (below baseline)


                    Outpatient Respiratory Illness: Activity Map
                    This week, 2 jurisdictions experienced moderate activity and 1 jurisdiction experienced high or very high activity.

                    Long-term Care Facilities0.2%


                    of facilities reported
                    ≥ 1 influenza-positive test
                    among residents this week.

                    Severe Disease


                    FluSurv-NET
                    Hospitalization rates will be updated starting later this season.

                    HHS Protect Hospitalizations495


                    patients admitted to hospitals with influenza
                    this week.


                    NCHS Mortality15.5%


                    of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

                    Pediatric Deaths0


                    influenza-associated deaths occurring
                    this season


                    All data are preliminary and may change as more reports are received.

                    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                    Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

                    Key Points
                    • Influenza activity remains low nationally, but is slowly increasing.
                    • The number of influenza viruses detected by clinical and public health labs has increased in recent weeks. The majority of viruses detected are A(H3N2). Just over 80% have occurred among children and young adults aged 5-24 years.
                    • The percentage of outpatient visits due to respiratory illness has trended upwards in recent weeks but remains below baseline.
                    • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
                    • As of Nov. 19, 2021, 166.9M doses of flu vaccine have been distributed in the U.S.
                    • Flu vaccines are available at many different locations, including pharmacies and health departments. Visit www.vaccines.gov to find a flu vaccine near you.
                    • There are also flu antiviral drugs that can be used to treat flu illness.
                    U.S. Virologic Surveillance


                    Overall, influenza activity is still low; however, an increasing number of influenza positive tests have been reported by clinical and public health laboratories during recent weeks. The majority are influenza A(H3N2). Influenza A(H3N2) viruses have been reported by public health laboratories in all 10 HHS regions this season. So far during the 2021-22 season, 1,034 (81.2%) of the 1,274 A(H3N2) viruses with known patient age were reported among children and young adults aged 5-24 years. For regional and state level data about circulating influenza viruses, please visit FluView Interactive.
                    Clinical Laboratories


                    The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

                    No. of specimens tested 43,267 392,541
                    No. of positive specimens (%) 632 (1.5%) 2,023 (0.5%)
                    Positive specimens by type
                    Influenza A 608 (96.2%) 1,766 (87.3%)
                    Influenza B 24 (3.8%) 257 (12.7%)

                    View Chart Data | View Full ScreenPublic Health Laboratories


                    The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
                    No. of specimens tested 14,399 165,808
                    No. of positive specimens 332 1,573
                    Positive specimens by type/subtype
                    Influenza A 330 (99.4%) 1,519 (96.6%)
                    (H1N1)pdm09 1 (0.4%) 4 (0.3%)
                    H3N2 248 (99.6%) 1,294 (99.6%)
                    H3N2v 0 1 (0.1%)
                    Subtyping not performed 81 220
                    Influenza B 2 (0.6%) 54 (3.4%)
                    Yamagata lineage 1 (50%) 5 (16.1%)
                    Victoria lineage 1 (50%) 26 (83.9%)
                    Lineage not performed 0 23



                    View Chart Data | View Full Screen

                    Additional virologic surveillance information for current and past seasons:
                    Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
                    Influenza Virus Characterization


                    CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

                    Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
                    Outpatient Respiratory Illness Surveillance


                    The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms such as influenza, SARS-CoV-2, and RSV. Due to the COVID-19 pandemic, health care-seeking behaviors have changed, and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
                    Outpatient Respiratory Illness Visits


                    Nationwide during week 47, 2.4% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This percentage is below the national baseline of 2.5%. Regions 3 and 7 are above their region-specific baselines; all other regions are below their baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI can vary by location.



                    * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


                    View Chart Data (current season only) | View Full ScreenOutpatient Respiratory Illness Visits by Age Group


                    More than 70% of ILINet participants provide both the number of patient visits for respiratory illness and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for respiratory illness by age group.

                    The percentage of visits for respiratory illness reported in ILINet are trending upward for four age groups (0–4 years, 5–24 years, 25-49 years and 50–64 years) and remains stable for those 65+ years.



                    * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

                    View Chart Data | View Full Screen
                    Outpatient Respiratory Illness Activity Map


                    Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
                    Week 47
                    (Week ending
                    Nov. 27, 2021)
                    Week 46
                    (Week ending
                    Nov. 20, 2021)
                    Week 47
                    (Week ending
                    Nov. 27, 2021)
                    Week 46
                    (Week ending
                    Nov. 20, 2021)
                    Very High 0 0 0 2
                    High 1 3 18 20
                    Moderate 2 3 42 42
                    Low 23 10 141 112
                    Minimal 28 39 437 479
                    Insufficient Data 1 0 291 274



                    *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

                    Additional information about medically attended visits for ILI for current and past seasons:
                    Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
                    Long-term Care Facility (LTCF) Surveillance


                    LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 47, 30 (0.2%) of 14,001 reporting LTCFs reported at least one influenza positive test among their residents.



                    View Chart Dataexcel icon | View Full Screen

                    Additional information about long-term care facility surveillance:
                    Surveillance Methods | Additional Dataexternal icon
                    Hospitalization Surveillance

                    FluSurv-NET


                    The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

                    Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
                    Surveillance Methods | FluView Interactive
                    HHS-Protect Hospitalization Surveillance


                    Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 47, 495 patients with laboratory-confirmed influenza were admitted to the hospital.



                    View Chart Dataexcel icon | View Full Screen

                    Additional HHS Protect hospitalization surveillance information:
                    Surveillance Methods | Additional Dataexternal icon
                    Mortality Surveillance

                    National Center for Health Statistics (NCHS) Mortality Surveillance


                    Based on NCHS mortality surveillance data available on December 2, 2021, 15.5% of the deaths that occurred during the week ending November 27, 2021 (week 47), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.4% for this week. Among the 2,505 PIC deaths reported for this week, 1,826 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and four listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



                    View Chart Dataexcel icon | View Full Screen

                    Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
                    Surveillance Methods | FluView Interactive
                    Influenza-Associated Pediatric Mortality


                    No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


                    View Full Screen

                    Additional pediatric mortality surveillance information for current and past seasons:
                    Surveillance Methods | FluView Interactive


                    Additional National and International Influenza Surveillance Information


                    FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

                    National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

                    U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
                    Additional influenza surveillance information from participating WHO member nations is available through
                    FluNetexternal icon and the Global Epidemiology Reports.external icon

                    WHO Collaborating Centers for Influenza:
                    Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

                    Europe:
                    The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

                    Public Health Agency of Canada:
                    The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

                    Public Health England:
                    The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

                    Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

                    A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                    Page last reviewed: December 3, 2021, 01:00 PM

                    https://www.cdc.gov/flu/weekly/index.htm

                    Comment


                    • #11
                      bump this

                      Comment


                      • #12

                        Weekly U.S. Influenza Surveillance Report


                        Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

                        Key Updates for Week 48, ending December 4, 2021

                        Seasonal influenza activity in the United States remains low but continues to increase.
                        Viruses


                        Clinical Lab2.6%


                        positive for influenza
                        this week


                        Public Health Lab
                        A small but increasing
                        number of specimens have
                        tested positive. The majority of viruses detected are influenza A(H3N2).


                        Virus Characterization
                        Influenza virus characterization information will be reported later this season.
                        Illness

                        Outpatient Respiratory Illness2.5%


                        of visits to a health care provider for respiratory illness this week
                        (at baseline)


                        Outpatient Respiratory Illness: Activity Map
                        This week, 6 jurisdictions experienced moderate activity and 1 jurisdiction experienced high or very high activity.

                        Long-term Care Facilities0.4%


                        of facilities reported
                        ≥ 1 influenza-positive test
                        among residents this week.

                        Severe Disease


                        FluSurv-NET
                        Hospitalization rates will be updated starting later this season.

                        HHS Protect Hospitalizations841


                        patients admitted to hospitals with influenza
                        this week.


                        NCHS Mortality17.5%


                        of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

                        Pediatric Deaths0


                        influenza-associated deaths occurring
                        this season


                        All data are preliminary and may change as more reports are received.

                        A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                        Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

                        Key Points
                        • Influenza activity remains low nationally but continues to increase.
                        • The number of influenza viruses detected by clinical and public health labs has increased in recent weeks. The majority of viruses detected are A(H3N2). Most influenza A(H3N2) infections have occurred among children and young adults ages 5-24 years; however, the proportion of infections occurring among adults age 25 years and older has increased in recent weeks.
                        • The percentage of outpatient visits due to respiratory illness has trended upwards in recent weeks and is now at the national baseline. While influenza is contributing to levels of respiratory illness, other respiratory viruses are circulating. The relative contribution of influenza to respiratory illness varies by location.
                        • Laboratory-confirmed flu activity is increasing but remains relatively low, confirming that other respiratory viruses are contributing to respiratory disease.
                        • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
                        • There are early signs that flu vaccination uptake is down this season compared to last.
                        • Flu vaccines are available at many different locations, including pharmacies and health departments. With flu activity just getting started, there is still time to benefit from flu vaccination this season. Visit www.vaccines.gov to find a flu vaccine near you.
                        • There are also flu antiviral drugs that can be used to treat flu illness.
                        U.S. Virologic Surveillance


                        Overall, influenza activity is still low; however, an increasing number of influenza positive tests have been reported by clinical and public health laboratories during recent weeks. Influenza A(H3N2) has been the most frequently detected. The majority of influenza A(H3N2) viruses were detected in persons aged 5-24 years old, but the proportion of influenza A(H3N2) virus detections occurring among adults aged 25 years and older has increased in recent weeks. Influenza A(H3N2) viruses were reported by public health laboratories in all 10 HHS regions this week. For regional and state level data about circulating influenza viruses, please visit FluView Interactive. Viruses known to be associated with recent live attenuated influenza vaccine (LAIV) receipt or found upon further testing to be a vaccine virus are not included as they are not circulating influenza viruses.
                        Clinical Laboratories


                        The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

                        No. of specimens tested 58,767 480,224
                        No. of positive specimens (%) 1,532 (2.6%) 3,905 (0.8%)
                        Positive specimens by type
                        Influenza A 1,489 (97.2%) 3,592 (92.0%)
                        Influenza B 43 (2.8%) 313 (8.0%)

                        View Chart Data | View Full ScreenPublic Health Laboratories


                        The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
                        No. of specimens tested 22,062 188,827
                        No. of positive specimens 567 2,373
                        Positive specimens by type/subtype
                        Influenza A 562 (99.1%) 2,314 (97.5%)
                        (H1N1)pdm09 0 4 (0.2%)
                        H3N2 409 (100%) 1,952 (99.7%)
                        H3N2v 0 1 (0.1%)
                        Subtyping not performed 153 357
                        Influenza B 5 (0.9%) 59 (2.5%)
                        Yamagata lineage 0 1 (3.3%)
                        Victoria lineage 3 (100%) 29 (96.7%)
                        Lineage not performed 2 29



                        View Chart Data | View Full Screen

                        Additional virologic surveillance information for current and past seasons:
                        Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
                        Influenza Virus Characterization


                        CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

                        Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
                        Outpatient Respiratory Illness Surveillance


                        The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms such as influenza, SARS-CoV-2, and RSV. Due to the COVID-19 pandemic, health care-seeking behaviors have changed, and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
                        Outpatient Respiratory Illness Visits


                        Nationwide, during week 48, 2.5% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This percentage is at the national baseline. Regions 1, 2, 3 and 7 are above their region-specific baselines; all other regions are below their baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI can vary by location.



                        * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


                        View Chart Data (current season only) | View Full ScreenOutpatient Respiratory Illness Visits by Age Group


                        More than 70% of ILINet participants provide both the number of patient visits for respiratory illness and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for respiratory illness by age group.

                        The percentage of visits for respiratory illness reported in ILINet are trending upward for all age groups (0–4 years, 5–24 years, 25-49 years, 50–64 years, and 65+).



                        * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

                        View Chart Data | View Full Screen
                        Outpatient Respiratory Illness Activity Map


                        Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
                        Week 48
                        (Week ending
                        Dec. 8, 2021)
                        Week 47
                        (Week ending
                        Nov. 27, 2021)
                        Week 48
                        (Week ending
                        Dec. 8, 2021)
                        Week 47
                        (Week ending
                        Nov. 27, 2021)
                        Very High 0 0 2 0
                        High 1 1 18 19
                        Moderate 6 3 62 46
                        Low 16 21 157 148
                        Minimal 31 29 420 453
                        Insufficient Data 1 1 270 263



                        *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

                        Additional information about medically attended visits for ILI for current and past seasons:
                        Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
                        Long-term Care Facility (LTCF) Surveillance


                        LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 48, 55 (0.4%) of 14,237 reporting LTCFs reported at least one influenza positive test among their residents.



                        View Chart Dataexcel icon | View Full Screen

                        Additional information about long-term care facility surveillance:
                        Surveillance Methods | Additional Dataexternal icon
                        Hospitalization Surveillance

                        FluSurv-NET


                        The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET estimated hospitalization rates will be updated weekly starting later this season.

                        Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
                        Surveillance Methods | FluView Interactive
                        HHS-Protect Hospitalization Surveillance


                        Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 48, 841 patients with laboratory-confirmed influenza were admitted to the hospital.



                        View Chart Dataexcel icon | View Full Screen

                        Additional HHS Protect hospitalization surveillance information:
                        Surveillance Methods | Additional Dataexternal icon
                        Mortality Surveillance

                        National Center for Health Statistics (NCHS) Mortality Surveillance


                        Based on NCHS mortality surveillance data available on December 9, 2021, 17.5% of the deaths that occurred during the week ending December 4, 2021 (week 48), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.5% for this week. Among the 3,167 PIC deaths reported for this week, 2,374 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and five listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



                        View Chart Dataexcel icon | View Full Screen

                        Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
                        Surveillance Methods | FluView Interactive
                        Influenza-Associated Pediatric Mortality


                        No influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


                        View Full Screen

                        Additional pediatric mortality surveillance information for current and past seasons:
                        Surveillance Methods | FluView Interactive


                        Additional National and International Influenza Surveillance Information


                        FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

                        National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

                        U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
                        Additional influenza surveillance information from participating WHO member nations is available through
                        FluNetexternal icon and the Global Epidemiology Reports.external icon

                        WHO Collaborating Centers for Influenza:
                        Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

                        Europe:
                        The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

                        Public Health Agency of Canada:
                        The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

                        Public Health England:
                        The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

                        Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

                        A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                        Page last reviewed: December 10, 2021, 11:00 am

                        https://www.cdc.gov/flu/weekly/index.htm

                        Comment


                        • #13
                          bump this

                          Comment


                          • #14

                            Weekly U.S. Influenza Surveillance Report


                            Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

                            Key Updates for Week 49, ending December 11, 2021

                            Seasonal influenza activity in the United States is increasing, including indicators that track hospitalizations. The amount of activity varies by region.
                            Viruses


                            Clinical Lab3.5%


                            positive for influenza
                            this week


                            Public Health Lab
                            The majority of viruses
                            detected are influenza A(H3N2).


                            Virus Characterization
                            Influenza virus characterization information will be reported later this season.
                            Illness

                            Outpatient Respiratory Illness2.7%


                            of visits to a health care provider are for respiratory illness this week
                            (above baseline)


                            Outpatient Respiratory Illness: Activity Map
                            This week, 10 jurisdictions experienced moderate activity and 2 jurisdiction experienced high or very high activity.

                            Long-term Care Facilities0.5%


                            of facilities reported
                            ≥ 1 influenza-positive test
                            among residents this week.

                            Severe Disease


                            FluSurv-NET
                            Hospitalization rates will be updated starting later this season.

                            HHS Protect Hospitalizations1,057


                            patients admitted to hospitals with influenza
                            this week.


                            NCHS Mortality17.4%


                            of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

                            Pediatric Deaths0


                            influenza-associated deaths occurring
                            this season


                            All data are preliminary and may change as more reports are received.

                            A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                            Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

                            Key Points
                            • Influenza activity is increasing, with the eastern and central parts of the country seeing the largest increases and the western part of the country reporting lower levels of influenza virus circulation at this time.
                            • The majority of influenza viruses detected are A(H3N2). Most influenza A(H3N2) infections have occurred among children and young adults ages 5-24 years; however, the proportion of infections occurring among adults age 25 years and older has been increasing.
                            • Hospitalizations for influenza are starting to increase.
                            • The percentage of outpatient visits due to respiratory illness has trended upwards in recent weeks and is now above the national baseline. Influenza is contributing to levels of respiratory illness, but other respiratory viruses are also circulating. The relative contribution of influenza to respiratory illness varies by location.
                            • The flu season is just getting started. It’s not too late to get vaccinated. An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
                            • There are early signs that flu vaccination uptake is down this season compared to last.
                            • Flu vaccines are available at many different locations, including pharmacies and health departments. With flu activity just getting started, there is still time to benefit from flu vaccination this season. Visit www.vaccines.gov to find a flu vaccine near you.
                            • There are also flu antiviral drugs that can be used to treat flu illness
                            U.S. Virologic Surveillance


                            An increasing number of influenza positive tests have been reported by clinical and public health laboratories during recent weeks. Influenza A(H3N2) viruses have been the most frequently detected. The majority of influenza A(H3N2) viruses were detected in persons aged 5-24 years old, but the proportion of influenza A(H3N2) virus detections occurring among adults aged 25 years and older has increased in recent weeks. Influenza A(H3N2) viruses were reported by public health laboratories in all 10 HHS regions this week. For regional and state level data about circulating influenza viruses, please visit FluView Interactive. Viruses known to be associated with recent live attenuated influenza vaccine (LAIV) receipt or found upon further testing to be a vaccine virus are not included as they are not circulating influenza viruses.
                            Clinical Laboratories


                            The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

                            No. of specimens tested 70,157 588,384
                            No. of positive specimens (%) 2,438 (3.5%) 7,516 (1.3%)
                            Positive specimens by type
                            Influenza A 2,405 (98.6%) 7,138 (95.0%)
                            Influenza B 33 (1.4%) 378 (5.0%)

                            View Chart Data | View Full ScreenPublic Health Laboratories


                            The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
                            No. of specimens tested 23,849 217,285
                            No. of positive specimens 485 3,127
                            Positive specimens by type/subtype
                            Influenza A 485 (100%) 3,068 (98.1%)
                            (H1N1)pdm09 0 4 (0.2%)
                            H3N2 279 (100%) 2,499 (99.8%)
                            H3N2v 0 1 (<0.1%)
                            Subtyping not performed 206 564
                            Influenza B 0 (0%) 59 (1.9%)
                            Yamagata lineage 0 1 (3.3%)
                            Victoria lineage 0 29 (96.7%)
                            Lineage not performed 0 29



                            View Chart Data | View Full Screen

                            Additional virologic surveillance information for current and past seasons:
                            Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
                            Influenza Virus Characterization


                            CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines and to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

                            Virus characterization data will be updated later this season when a sufficient number of specimens have been tested.
                            Outpatient Respiratory Illness Surveillance


                            The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms such as influenza, SARS-CoV-2, and RSV. Due to the COVID-19 pandemic, health care-seeking behaviors have changed, and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
                            Outpatient Respiratory Illness Visits


                            Nationwide, during week 49, 2.7% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This percentage is above the national baseline. Regions 1, 2, 3, 4, and 7 are above their region-specific baselines; all other regions are below their baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI can vary by location.



                            * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


                            View Chart Data (current season only) | View Full ScreenOutpatient Respiratory Illness Visits by Age Group


                            More than 70% of ILINet participants provide both the number of patient visits for respiratory illness and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for respiratory illness by age group.

                            The percentage of visits for respiratory illness reported in ILINet are trending upward for all age groups (0–4 years, 5–24 years, 25-49 years, 50–64 years, and 65+).



                            * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

                            View Chart Data | View Full Screen
                            Outpatient Respiratory Illness Activity Map


                            Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
                            Week 49
                            (Week ending
                            Dec. 11, 2021)
                            Week 48
                            (Week ending
                            Dec. 4, 2021)
                            Week 49
                            (Week ending
                            Dec. 11, 2021)
                            Week 48
                            (Week ending
                            Dec. 4, 2021)
                            Very High 0 0 2 1
                            High 2 1 24 20
                            Moderate 10 6 63 63
                            Low 19 16 162 156
                            Minimal 23 31 408 436
                            Insufficient Data 1 1 270 253



                            *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

                            Additional information about medically attended visits for ILI for current and past seasons:
                            Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
                            Long-term Care Facility (LTCF) Surveillance


                            LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 49, 71 (0.5%) of 14,268 reporting LTCFs reported at least one influenza positive test among their residents.



                            View Chart Dataexcel icon | View Full Screen

                            Additional information about long-term care facility surveillance:
                            Surveillance Methods | Additional Dataexternal icon
                            Hospitalization Surveillance

                            FluSurv-NET


                            The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in the Emerging Infections Program (EIP) states and Influenza Hospitalization Surveillance Project (IHSP) states.

                            A total of 242 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1, 2021, and December 11, 2021. This is more than the total number of hospitalizations reported during the 2020-2021 season, and similar to the number of hospitalizations seen at this point during the 2015-16 season. Hospitalization rates will be presented once case counts increase to a level that produces stable rates.

                            Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
                            Surveillance Methods | FluView Interactive
                            HHS-Protect Hospitalization Surveillance


                            Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 49, 1,057 patients with laboratory-confirmed influenza were admitted to the hospital.



                            View Chart Dataexcel icon | View Full Screen

                            Additional HHS Protect hospitalization surveillance information:
                            Surveillance Methods | Additional Dataexternal icon
                            Mortality Surveillance

                            National Center for Health Statistics (NCHS) Mortality Surveillance


                            Based on NCHS mortality surveillance data available on December 16, 2021, 17.4% of the deaths that occurred during the week ending December 11, 2021 (week 49), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.6% for this week. Among the 3,330 PIC deaths reported for this week, 2,569 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and eight listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



                            View Chart Dataexcel icon | View Full Screen

                            Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
                            Surveillance Methods | FluView Interactive
                            Influenza-Associated Pediatric Mortality


                            As of week 49, no influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


                            View Full Screen

                            Additional pediatric mortality surveillance information for current and past seasons:
                            Surveillance Methods | FluView Interactive


                            Additional National and International Influenza Surveillance Information


                            FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

                            National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

                            U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
                            Additional influenza surveillance information from participating WHO member nations is available through
                            FluNetexternal icon and the Global Epidemiology Reports.external icon

                            WHO Collaborating Centers for Influenza:
                            Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

                            Europe:
                            The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

                            Public Health Agency of Canada:
                            The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

                            Public Health England:
                            The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

                            Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

                            A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                            Page last reviewed: December 17, 2021, 11:00 AM


                            https://www.cdc.gov/flu/weekly/index.htm

                            Comment


                            • #15

                              Weekly U.S. Influenza Surveillance Report


                              Note: CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review.

                              Key Updates for Week 51, ending December 25, 2021

                              Seasonal influenza activity in the United States is increasing, including indicators that track hospitalizations. The amount of activity varies by region.
                              Viruses


                              Clinical Lab6.2%


                              positive for influenza
                              this week


                              Public Health Lab
                              The majority of viruses
                              detected are influenza A(H3N2).


                              Virus Characterization
                              Genetic characterization data are now being reported.
                              Illness

                              Outpatient Respiratory Illness3.8%


                              of visits to a health care provider are for respiratory illness this week
                              (above baseline)


                              Outpatient Respiratory Illness: Activity Map
                              This week, 12 jurisdictions experienced moderate activity and 19 jurisdictions experienced high or very high activity.

                              Long-term Care Facilities0.9%


                              of facilities reported
                              ≥ 1 influenza-positive test
                              among residents this week.

                              Severe Disease


                              FluSurv-NET1.8 per 100,000


                              cumulative hospitalization rate

                              HHS Protect Hospitalizations1,825


                              patients admitted to hospitals with influenza
                              this week.


                              NCHS Mortality19.2%


                              of deaths attributed to pneumonia, influenza, or COVID-19 this week (above threshold)

                              Pediatric Deaths0


                              influenza-associated deaths reported this week

                              All data are preliminary and may change as more reports are received.

                              A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                              Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.

                              Key Points
                              • Influenza activity is increasing, with the eastern and central parts of the country seeing the majority of viruses reported and the western part of the country reporting lower levels of influenza virus circulation.
                              • The majority of influenza viruses detected are A(H3N2). Most influenza A(H3N2) infections have occurred among children and young adults ages 5-24 years; however, the proportion of infections occurring among adults age 25 years and older has been increasing.
                              • While there are little data to date, most of the H3N2 viruses so far are genetically closely related to the vaccine virus, but there are some antigenic differences that have developed as H3N2 viruses have continued to evolve.
                              • The percentage of outpatient visits due to respiratory illness is trending upwards and is above the national baseline. Influenza is contributing to levels of respiratory illness, but other respiratory viruses are also circulating. The relative contribution of influenza varies by location.
                              • Hospitalizations for influenza are starting to increase.
                              • The flu season is just getting started. There’s still time to get vaccinated. An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
                              • There are early signs that flu vaccination uptake is down this season compared to last.
                              • Flu vaccines are available at many different locations, including pharmacies and health departments. With flu activity just getting started, there is still time to benefit from flu vaccination this season. Visit www.vaccines.gov to find a flu vaccine near you.
                              • There are also flu antiviral drugs that can be used to treat flu illness.
                              U.S. Virologic Surveillance


                              The week 51 virologic data may have been impacted by delays in reporting due to the holiday therefore, percent positivity and testing numbers should be interpreted with caution. An increasing number of influenza positive tests have been reported by clinical and public health laboratories during recent weeks. Influenza A(H3N2) viruses have been the most frequently detected. Persons aged 5-24 years old account for the largest proportion of influenza A(H3N2) viruses detected, but the proportion of influenza A(H3N2) virus detections occurring among other age groups has increased in recent weeks. Influenza A(H3N2) viruses were reported by public health laboratories in all HHS regions except for Region 10 this week. For regional and state level data about circulating influenza viruses, please visit FluView Interactive. Viruses known to be associated with recent live attenuated influenza vaccine (LAIV) receipt or found upon further testing to be a vaccine virus are not included as they are not circulating influenza viruses.
                              Clinical Laboratories


                              The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

                              No. of specimens tested 70,660 778,091
                              No. of positive specimens (%) 4,393 (6.2%) 18,479 (2.4%)
                              Positive specimens by type
                              Influenza A 4,337 (98.7%) 17,985 (97.3%)
                              Influenza B 57 (1.3%) 494 (2.7%)

                              View Chart Data | View Full ScreenPublic Health Laboratories


                              The results of tests performed by public health laboratories nationwide are summarized below. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza subtype/lineage.
                              No. of specimens tested 29,486 282,321
                              No. of positive specimens 634 5,357
                              Positive specimens by type/subtype
                              Influenza A 632 (99.7%) 5,294 (98.8%)
                              (H1N1)pdm09 0 4 (<0.1%)
                              H3N2 375 (100%) 4,110 (99.9%)
                              H3N2v 0 1 (<0.1%)
                              Subtyping not performed 257 1,179
                              Influenza B 2 (0.3%) 63 (1.2%)
                              Yamagata lineage 0 1 (3.3%)
                              Victoria lineage 0 29 (96.7%)
                              Lineage not performed 2 33



                              View Chart Data | View Full Screen

                              Additional virologic surveillance information for current and past seasons:
                              Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data
                              Influenza Virus Characterization


                              CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local public health laboratories using Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are to the reference viruses representing viruses contained in the current influenza vaccines. The data are also used to monitor evolutionary changes that continually occur in influenza viruses circulating in humans. CDC also tests susceptibility of circulating influenza viruses to antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir.

                              CDC genetically characterized 208 influenza viruses collected since October 3, 2021. While there are little data to date, most of the H3N2 viruses so far are genetically closely related to the vaccine virus, but there are some antigenic differences that have developed as H3N2 viruses have continued to evolve. Virus antigenic and antiviral susceptibility data will be reported later this season when a sufficient number of specimens have been tested.

                              CDC genetically characterized 108 influenza viruses collected October 3, 2021 to present:
                              A/H1 3
                              6B.1A 3 (100%) 5a.1 2 (67%)
                              5a.2 1 (33%)
                              A/H3 184
                              3C.2a1b 189 (100%) 1a 0
                              1b 1 (1%)
                              2a 0
                              2a.1 0
                              2a.2 183 (99%)
                              3C.3a 0 3a 0
                              B/Victoria 16
                              V1A 16 (100%) V1A 0
                              V1A.1 0
                              V1A.3 9 (56%)
                              V1A.3a 0
                              V1A.3a.1 0
                              V1A.3a.2 7 (44%)
                              B/Yamagata 0
                              Y3 0
                              CDC assesses susceptibility of influenza viruses to the antiviral medications including the neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) and the PA endonuclease inhibitor baloxavir using next generation sequence analysis supplemented by laboratory assays. Information about antiviral susceptibility test methods can be found at U.S. Influenza Surveillance: Purpose and Methods | CDC.

                              Viruses collected in the United States since October 3, 2021, were tested for antiviral susceptibility as follows:
                              Neuraminidase
                              Inhibitors
                              Oseltamivir Viruses
                              Tested
                              210 3 191 16 0
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              Highly
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              Peramivir Viruses
                              Tested
                              210 3 191 16 0
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              Highly
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              Zanamivir Viruses
                              Tested
                              210 3 191 16 0
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              Highly
                              Reduced
                              Inhibition
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              PA Cap-Dependent Endonuclease Inhibitor Baloxavir Viruses
                              Tested
                              193 3 174 16 0
                              Reduced
                              Susceptibility
                              (0.0%) (0.0%) (0.0%) (0.0%) (0.0%)
                              High levels of resistance to the adamantanes (amantadine and rimantadine) persist among influenza A(H1N1)pdm09 and influenza A(H3N2) viruses (the adamantanes are not effective against influenza B viruses). Therefore, use of these antivirals for treatment and prevention of influenza A virus infection is not recommended and data from adamantane resistance testing are not presented.
                              Outpatient Respiratory Illness Surveillance


                              The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms such as influenza, SARS-CoV-2, and RSV. Due to the COVID-19 pandemic, health care-seeking behaviors have changed, and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.
                              Outpatient Respiratory Illness Visits


                              Nationwide, during week 51, 3.8% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This percentage is above the national baseline. Nine of the 10 HHS regions are above their region-specific baselines; only Region 6 is below their baseline. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.



                              * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”


                              View Chart Data (current season only) | View Full ScreenOutpatient Respiratory Illness Visits by Age Group


                              More than 70% of ILINet participants provide both the number of patient visits for respiratory illness and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for respiratory illness by age group.

                              The percentage of visits for respiratory illness reported in ILINet increased for all age groups (0–4 years, 5–24 years, 25-49 years, 50–64 years, and 65+).



                              * Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

                              View Chart Data | View Full Screen
                              Outpatient Respiratory Illness Activity Map


                              Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).
                              Week 51
                              (Week ending
                              Dec. 25, 2021)
                              Week 50
                              (Week ending
                              Dec. 18, 2021)
                              Week 51
                              (Week ending
                              Dec. 25, 2021)
                              Week 50
                              (Week ending
                              Dec. 18, 2021)
                              Very High 3 0 7 3
                              High 16 8 83 49
                              Moderate 12 14 104 79
                              Low 13 13 167 163
                              Minimal 9 20 280 365
                              Insufficient Data 2 0 288 270



                              *Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.

                              Additional information about medically attended visits for ILI for current and past seasons:
                              Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
                              Long-term Care Facility (LTCF) Surveillance


                              LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 51, 122 (0.9%) of 14,084 reporting LTCFs reported at least one influenza positive test among their residents.



                              View Chart Dataexcel icon | View Full Screen

                              Additional information about long-term care facility surveillance:
                              Surveillance Methods | Additional Dataexternal icon
                              Hospitalization Surveillance

                              FluSurv-NET


                              The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population.

                              A total of 535 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1, 2021, and December 25, 2021, with a cumulative hospitalization rate of 1.8 per 100,000 population, which is more than double the overall cumulative hospitalization rate reported during the 2020-2021 season.

                              FluSurv-NET hospitalization data are preliminary. Case counts and rates for recent hospital admissions are subject to reporting delays; these delays are likely to be more pronounced around holidays. As data are received each week, prior case counts and rates are updated accordingly.

                              Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
                              Surveillance Methods | FluView Interactive
                              HHS-Protect Hospitalization Surveillance


                              Hospitals report to HHS-Protect the number of patients admitted with laboratory-confirmed influenza. During week 51, 1,825 patients with laboratory-confirmed influenza were admitted to the hospital.



                              View Chart Dataexcel icon | View Full Screen

                              Additional HHS Protect hospitalization surveillance information:
                              Surveillance Methods | Additional Dataexternal icon
                              Mortality Surveillance

                              National Center for Health Statistics (NCHS) Mortality Surveillance


                              Based on NCHS mortality surveillance data available on December 30, 2021, 19.2% of the deaths that occurred during the week ending December 25, 2021 (week 51), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.8% for this week. Among the 3,381 PIC deaths reported for this week, 2,582 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and 12 listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not influenza. The data presented are preliminary and may change as more data are received and processed.



                              View Chart Dataexcel icon | View Full Screen

                              Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
                              Surveillance Methods | FluView Interactive
                              Influenza-Associated Pediatric Mortality


                              No influenza-associated pediatric deaths were reported to CDC during week 51.

                              A total of two influenza-associated pediatric deaths occurring during the 2021-2022 season have been reported to CDC.


                              View Full Screen

                              Additional pediatric mortality surveillance information for current and past seasons:
                              Surveillance Methods | FluView Interactive


                              Additional National and International Influenza Surveillance Information


                              FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

                              National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

                              U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information. World Health Organization:
                              Additional influenza surveillance information from participating WHO member nations is available through
                              FluNetexternal icon and the Global Epidemiology Reports.external icon

                              WHO Collaborating Centers for Influenza:
                              Australiaexternal icon, Chinaexternal icon, Japanexternal icon, the United Kingdomexternal icon, and the United States (CDC in Atlanta, Georgia)

                              Europe:
                              The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Controlexternal icon.

                              Public Health Agency of Canada:
                              The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch reportexternal icon.

                              Public Health England:
                              The most up-to-date influenza information from the United Kingdom is available from Public Health Englandexternal icon.

                              Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

                              A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.

                              Page last reviewed: December 27, 2021, 11:00 AM

                              https://www.cdc.gov/flu/weekly/index.htm

                              Comment

                              Working...
                              X