US FluView - Weekly Surveillance Flu report 2026/2027 season - for trend analysis

[Lance]

Weekly US Influenza Surveillance Report: Key Updates for Week 38, ending September 26, 2026​

For Everyone
Oct. 2, 2026, visit link for details.

Key points​

Seasonal influenza activity remains low nationally, but is increasing.

U.S. virologic surveillance​

Clinical Laboratories​

Nationally, during Week 38, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories was 3.4%. 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.

	Week 38	Data Cumulative since September 28, 2025 (Week 40)
No. of specimens tested	33,547	3,159,585
No. of positive specimens (%)	1,151 (3.4%)	327,476 (10.4%)
Positive specimens by type
Influenza A	1,108 (96.3%)	231,550 (70.7%)
Influenza B	43 (3.7%)	95,926 (29.3%)

Public 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 virus type/subtype/lineage. 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.

	Week 38	Data Cumulative since September 28, 2025 (Week 40)
No. of specimens tested	547	112,060
No. of positive specimens	79	68,721
Positive specimens by type/subtype
Influenza A	79 (100%)	57,618 (83.8%)
Subtyping Performed	55 (69.6%)	47,532 (82.5%)
(H1N1)pdm09	53 (96.4%)	7,548 (15.9%)
H3N2	2 (3.6%)	39,982 (84.1%)
H3N2v†	0	0
H5*	0	2 (<0.1%)
Subtyping not performed	24 (30.4%)	10,086 (17.5%)
Influenza B	0	11,103 (16.2%)
Lineage testing performed	0	4,581 (41.3%)
Yamagata lineage	0	0
Victoria lineage	0	4,581 (100%)
Lineage not performed	0	6,522 (58.7%)

*These data reflect specimens tested, and the number determined to be positive for influenza viruses at the public health labs (specimens tested are not the same as cases). The data does not reflect specimens tested only at CDC and could include more than one specimen tested per person. For more information on the number of people infected with A(H5) viruses, please visit the "How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation"

†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 exposure to swine, but person-to-person 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.

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 Infections​

No new confirmed human infections with a novel influenza virus were reported to CDC this week.

The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspected cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf.

An up-to-date summary of confirmed novel influenza virus cases is available at https://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.

An up-to-date summary of human cases of avian influenza A(H5) virus by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html.

Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm. A(H5N1) virus interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.

Additional information regarding human infections with novel influenza A viruses:​

Surveillance Methods | FluView Interactive

Outpatient and Emergency Department Illness Surveillance​

Outpatient Respiratory Illness Visits​

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and may capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza, SARS-CoV-2, and RSV. 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.

Nationwide during Week 38, 1.7% 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. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.


*Some calendar years do not include an epidemiologic Week 53. In those years, the Week 53 value shown is the average between Week 52 and Week 1.

**Effective October 3, 2021 (Week 40), the respiratory illness definition (fever plus cough or sore throat) no longer includes "without a known cause other than influenza."

View Chart Data

Outpatient 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.

During Week 38, the percentage of visits for respiratory illness reported in ILINet was 5.5% among those 0-4 years, 2.6% among those 5-24 years, 1.5% among those 25-49 years, 1.1% among those 50-64 years, and 0.8% among those 65 years and older.

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 38 (Week ending Sep. 26, 2026)	Week 37 (Week ending Sep. 19, 2026)	Week 38 (Week ending Sep. 26, 2026)	Week 37 (Week ending Sep. 19, 2026)
Activity Level	Number of Jurisdictions	Number of CBSAs
Very High	0	0	0	0
High	0	0	0	0
Moderate	0	0	7	6
Low	0	0	26	17
Minimal	55	55	657	675
Insufficient Data	0	0	239	231

*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

National Syndromic Surveillance System (NSSP)​

The overall percentage of emergency department (ED) visits with a discharge diagnosis of influenza reported in NSSP was 0.4% during Week 38. The percentage of visits by age group was 1.0% among those 0-4 years, 0.9% among those 5-17 years, 0.3% among those 18-64 years, and 0.4% among those 65 years and older.

RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season
2025-2026x
2024-2025x
Skip Over Chart Container

Age Group​

Skip Data Table
Data Table

Download Data (CSV)
Skipped data table.

Additional information about emergency department visits for flu for current and past seasons:‎‎‎​

Surveillance Methods | Emergency Department Visits for COVID-19, flu, and RSV

Hospitalization surveillance​

FluSurv-Net​

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 10% of the U.S. population. FluSurv-NET hospitalization data are preliminary. As data are received each week, prior case counts and rates are updated accordingly.

A total of 31,513 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1, 2025, and September 26, 2026. The weekly hospitalization rate observed during Week 38 was 0.5 per 100,000 population. The cumulative hospitalization rate observed in Week 38 was 90.0 per 100,000 population.

Additional FluSurv-NET data are available on FluView Interactive including hospitalization rates for the current and past seasons by age, sex, and race/ethnicity (http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html) as well as data on patient characteristics at: (http://gis.cdc.gov/grasp/fluview/FluHospChars.html.)

FluSurv-NET data are used to generate national estimates of the total numbers of influenza cases, medical visits, hospitalizations and deaths. This season, CDC is reporting preliminary cumulative in-season estimates, which are available at Estimated US Flu Disease Burden | Flu Burden | CDC.

Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:​

Surveillance Methods | FluView Interactive: Rates by Age, Sex, and Race/Ethnicity or Data on Patient Characteristics | RESP-NET Interactive

National Healthcare Safety Network (NHSN) Hospital Respiratory Data​

Hospitals report to NHSN the weekly number of patients with laboratory-confirmed influenza who were admitted to the hospital. Nationally, during Week 38, 2,572 (0.8 per 100,000 population) laboratory-confirmed influenza-associated hospitalizations were reported. When examining rates by age, the highest hospital admission rate per 100,000 population was among those 65+ years (2.6), followed by 50-64 years (0.8), and 0-4 years age group (0.6).

Additional NHSN Hospital Respiratory Data information:​

Surveillance Methods | Additional Data | FluView Interactive

National Healthcare Safety Network (NHSN) Long-Term Care Respiratory Pathogens & Vaccination Module​

Long-term care facilities (LTCFs [e.g., Nursing homes/skilled nursing facilities]) report respiratory pathogen (e.g., COVID-19, influenza, and RSV) data, including vaccination, cases, and hospitalizations among residents, to the NHSN Long-Term Care Respiratory Pathogens & Vaccination Module.

NHSN long-term care influenza hospitalization data are not included in summer FluView reports.

Mortality surveillance​

National Center for Health Statistics (NCHS) Mortality Surveillance​

Based on NCHS mortality surveillance data available on October 1, 2026, 0.1% of the deaths that occurred during the week ending September 26, 2026 (Week 38) were due to influenza. The data presented are preliminary and may change as more data are received and processed.

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 2025-2026 season were reported to CDC during Week 38.

A total of 195 influenza-associated pediatric deaths occurring during the 2025-2026 season have been reported to CDC.

Additional pediatric mortality surveillance information for current and past seasons:​

Surveillance Methods | FluView Interactive
All data in this report 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.

Weekly US Influenza Surveillance Report: Key Updates for Week 38, ending September 26, 2026

Seasonal influenza activity is low.

www.cdc.gov

 

[sharon sanders]

Weekly US Influenza Surveillance Report: Key Updates for Week 39, ending October 3, 2026​

For Everyone
Oct. 9, 2026, visit link for details.

Key points​

Seasonal influenza activity is increasing in many parts of the country but remains low.

Summary​

Key Points​

• Seasonal influenza activity remains low but has been increasing across multiple surveillance indicators since late August/early September, 2026.
  • The highest activity is occurring in the West Coast (HHS regions 9 and 10).
  • Every influenza season is different—some begin earlier than usual, others later. Early-season influenza activity is currently higher than typically observed at this time of year but remains within expected seasonal variation.*

• During Week 39, of the 204 influenza viruses reported by public health laboratories, 201 were influenza A and 3 were influenza B. Of the 127 influenza A viruses subtyped during Week 39, 125 (98.4%) were influenza A(H1N1)pdm09 and 2 (1.6%) were A(H3N2).
  • Since Week 21, 80.5% of the Influenza A viruses reported have been A(H1N1)pdm09 and among these, the majority have been D.3.1.1 HA subclade.
• Annual seasonal influenza (flu) vaccination is recommended. Influenza vaccines are available for persons aged 6 months and older. For most people influenza vaccination should ideally be offered before the end of October.
• There are prescription flu antiviral drugs that can treat flu illness; those should be started as early as possible and are especially important for patients at higher risk for influenza complications .1
• Influenza viruses are among several viruses contributing to respiratory disease activity. CDC is providing updated, integrated information about COVID-19, flu, and respiratory syncytial virus (RSV) activity on a weekly basis.

*The reporting period for each influenza season begins during epidemiologic Week 40 and ends Week 39 of the following year. Epidemiologic weeks refer to the sequential numbering of weeks (Sunday through Saturday) during a calendar year. This means that the exact start of the new influenza surveillance season varies slightly from season to season. The 2025-2026 influenza season began October 5, 2025, and ends on October 3, 2026. The new 2026-2027 influenza season begins October 4, 2026, and ends on October 2, 2027.

U.S. virologic surveillance​

Nationally and in HHS regions 1, 2, 3, 4, 7, 8, and 9, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories increased (change of ≥ 0.5 percentage points) compared to the previous week. In regions 5 and 6, the percentage remained stable but continued to trend upward. Although this proportion decreased in Region 10 compared to last week, this could be a result of a reduction in reporting. Percent positivity varied by region, ranging from 1.7% (Region 2) to 9.5% (Region 9). Influenza A(H1N1)pdm09 viruses were the most frequently reported by public health laboratories this week; however, the distribution of circulating viruses varied by region.

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.

	Week 39	Data Cumulative since September 28, 2025 (Week 40)
No. of specimens tested	39,317	3,210,542
No. of positive specimens (%)	1,435 (3.6%)	329,047 (10.2%)
Positive specimens by type
Influenza A	1,392 (97.0%)	233,173 (70.9%)
Influenza B	43 (3.0%)	95,874 (29.1%)

Public 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 virus type/subtype/lineage. 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.

	Week 39	Data Cumulative since September 28, 2025 (Week 40)
No. of specimens tested	691	113,791
No. of positive specimens	204	69,325
Positive specimens by type/subtype
Influenza A	201 (98.5%)	58,205 (84.0%)
Subtyping Performed	127 (63.2%)	48,052 (82.6%)
(H1N1)pdm09	125 (98.4%)	8,032 (16.7%)
H3N2	2 (1.6%)	40,018 (83.3%)
H3N2v†	0	0
H5*	0	2 (<0.1%)
Subtyping not performed	74 (36.8%)	10,153 (17.4%)
Influenza B	3 (1.5%)	11,120 (16.0%)
Lineage testing performed	0	4,582 (41.2%)
Yamagata lineage	0	0
Victoria lineage	0	4,582 (100%)
Lineage not performed	3 (100%)	6,538 (58.8%)

*These data reflect specimens tested, and the number determined to be positive for influenza viruses at the public health labs (specimens tested are not the same as cases). The data does not reflect specimens tested only at CDC and could include more than one specimen tested per person. For more information on the number of people infected with A(H5) viruses, please visit the "How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation"

†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 exposure to swine, but person-to-person 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.

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 Infections​

No new confirmed human infections with a novel influenza virus were reported to CDC this week.

The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspected cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf.

An up-to-date summary of confirmed novel influenza virus cases is available at https://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.

An up-to-date summary of human cases of avian influenza A(H5) virus by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html.

Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm. A(H5N1) virus interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.

Additional information regarding human infections with novel influenza A viruses:​

Surveillance Methods | FluView Interactive

Outpatient and Emergency Department Illness Surveillance​

Outpatient Respiratory Illness Visits​

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and may capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza, SARS-CoV-2, and RSV. 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.

Nationally, during Week 39, 1.8% 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 week’s percentage is below the national baseline of 3.1% and remained stable (change of ≤ 0.1 percentage points) compared to Week 38. However, ILI activity has been increasing slowly since late August/early September. HHS regions 4 and 10 increased (change of > 0.1 percentage points) and regions 1, 2, 3, 5, 6, 7, 8, and 9 remained stable (change of ≤ 0.1 percentage points) this week compared to the previous week. All 10 HHS regions are below their respective baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.


*Some calendar years do not include an epidemiologic Week 53. In those years, the Week 53 value shown is the average between Week 52 and Week 1.

**Effective October 3, 2021 (Week 40), the respiratory illness definition (fever plus cough or sore throat) no longer includes "without a known cause other than influenza."

Outpatient Respiratory Illness Visits by Age Group​

About 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. Based on these data, the percentage of visits for respiratory illness for the 0-4 years and 5-24 years age groups increased (change of > 0.1 percentage points) while the 25-49 years, 50-64 years, and 65 years and older age groups remained stable (change of ≤ 0.1 percentage point) in Week 39 compared to Week 38.

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 39 (Week ending Oct. 3, 2026)	Week 38 (Week ending Sep. 26, 2026)	Week 39 (Week ending Oct. 3, 2026)	Week 38 (Week ending Sep. 26, 2026)
Activity Level	Number of Jurisdictions	Number of CBSAs
Very High	0	0	0	0
High	0	0	4	0
Moderate	0	0	4	7
Low	2	0	33	26
Minimal	53	55	656	659
Insufficient Data	0	0	232	237

*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

National Syndromic Surveillance System (NSSP)​

The national percentage of emergency department (ED) visits with a discharge diagnosis (DD) of influenza reported in NSSP was 0.6% during Week 39 and remained stable (change of ≤ 0.1 percentage point) compared to the previous week but has been gradually increasing since early September. Nationally, the percentage of ED visits with a DD of influenza increased (change of > 0.1 percentage point) among the 0-4 years and 5-17 years age groups and remained stable among the 18-64 years and 65 years and older age groups. The percentage of ED visits with a DD of influenza increased this week compared to the previous week in HHS regions 4, 6, 9, and 10, and remained stable in all other regions (1, 2, 3, 5, 7, and 8). The age group trends varied by region.

RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season
2025-2026x
2024-2025x
Skip Over Chart Container

Age Group​

Skip Data Table
Data Table

Download Data (CSV)
Skipped data table.

Additional information about emergency department visits for flu for current and past seasons:‎‎‎​

Surveillance Methods | Emergency Department Visits for COVID-19, flu, and RSV

Hospitalization surveillance​

FluSurv-Net​

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 10% of the U.S. population. FluSurv-NET hospitalization data are preliminary. As data are received each week, prior case counts and rates are updated accordingly.

The weekly hospitalization rate observed during Week 39 was 0.6 per 100,000 population and has been increasing since August.

Additional FluSurv-NET data are available on FluView Interactive including hospitalization rates for the current and past seasons by age, sex, and race/ethnicity (http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html) as well as data on patient characteristics at: (http://gis.cdc.gov/grasp/fluview/FluHospChars.html.)

FluSurv-NET data are used to generate national estimates of the total numbers of influenza cases, medical visits, hospitalizations and deaths. This season, CDC is reporting preliminary cumulative in-season estimates, which are available at Estimated US Flu Disease Burden | Flu Burden | CDC.

Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:​

Surveillance Methods | FluView Interactive: Rates by Age, Sex, and Race/Ethnicity or Data on Patient Characteristics | RESP-NET Interactive

National Healthcare Safety Network (NHSN) Hospital Respiratory Data​

Hospitals report to NHSN the weekly number of patients with laboratory-confirmed influenza who were admitted to the hospital. Nationally, during Week 39, 3,334 laboratory-confirmed influenza-associated hospitalizations were reported. This week's influenza-associated hospital admission rate (1.0 per 100,000 population) increased (difference of ≥ 0.2) compared to Week 38, and hospital admission rates have been gradually increasing since early September.

Laboratory-confirmed influenza-associated hospital admission rates per 100,000 population increased in HHS regions 1, 4, 6, 7, 9, and 10 and remained stable in all other HHS regions this week compared to the previous week. Regional admission rates during Week 39 ranged from 0.5 (Region 1) to 1.4 (Region 10).

When examining rates by age for Week 39, the 0-4 and 65 years and older age groups increased and all other age groups remained stable compared to the previous week. The highest hospital admission rate per 100,000 population was among those 65 years and older (3.3), followed by the 50-64 years age group (0.9) and the 0-4 years age group (0.8).

Additional NHSN Hospital Respiratory Data information:​

Surveillance Methods | Additional Data | FluView Interactive

National Healthcare Safety Network (NHSN) Long-Term Care Respiratory Pathogens & Vaccination Module​

Beginning with the 2026–27 influenza season, NHSN long-term care influenza hospitalization data will no longer be reported in FluView. Previously reported LTC data and related information are available on the NHSN LTC webpage.

Mortality surveillance​

National Center for Health Statistics (NCHS) Mortality Surveillance​

Based on NCHS mortality surveillance data available on October 8, 2026, 0.1% of the deaths that occurred during the week ending October 3, 2026 (Week 39) were due to influenza. This percentage remained stable (< 0.1 percentage point change) compared to Week 38. The data presented are preliminary and may change as more data are received and processed.

Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:​

Surveillance Methods | FluView Interactive

Influenza-Associated Pediatric Mortality​

Three influenza-associated pediatric deaths occurring during the 2025-2026 season were reported to CDC during Week 39. The deaths occurred during weeks 51, 53, and 12 (the weeks ending December 20, 2025, January 3, 2026, and March 28, 2026).

A total of 198 influenza-associated pediatric deaths occurring during the 2025-2026 season have been reported to CDC.

Additional pediatric mortality surveillance information for current and past seasons:​

Surveillance Methods | FluView Interactive
All data in this report 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.

Additional National and International Influenza Surveillance Information​

Additional surveillance information​

West VirginiaFluView 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.

U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information.

state links

Alabama	Alaska	Arizona	Arkansas	California
Colorado	Connecticut	Delaware	District of Columbia	Florida
Georgia	Hawaii	Idaho	Illinois	Indiana
Iowa	Kansas	Kentucky	Louisiana	Maine
Maryland	Massachusetts	Michigan	Minnesota	Mississippi
Missouri	Montana	Nebraska	Nevada	New Hampshire
New Jersey	New Mexico	New York	North Carolina	North Dakota
Ohio	Oklahoma	Oregon	Pennsylvania	Rhode Island
South Carolina	South Dakota	Tennessee	Texas	Utah
Vermont	Virginia	Washington	West Virginia	Wisconsin
Wyoming	New York City	Puerto Rico	Virgin Islands

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

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

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.

Weekly US Influenza Surveillance Report: Key Updates for Week 39, ending October 3, 2026

Seasonal influenza activity is low.

www.cdc.gov

 

[Lance]

Weekly US Influenza Surveillance Report: Key Updates for Week 40, ending October 10, 2026​

For Everyone
Oct. 16, 2026, visit link for details.

Key Points​

• Seasonal influenza activity remains low but multiple surveillance indicators, including the percent of specimens testing positive for influenza, outpatient visits for influenza-like illness (ILI), emergency department (ED) visits with an influenza discharge diagnosis, and laboratory confirmed influenza associated hospitalizations have been increasing since late August/early September, 2026.
  • The highest activity is occurring in the West Coast (HHS regions 9 and 10).
  • Every influenza season is different—some begin earlier than usual, others later. Early-season influenza activity is currently higher than typically observed at this time of year but remains within expected seasonal variation.
• During Week 40 (the week ending October 10, 2026), of the 300 influenza viruses reported by public health laboratories, 292 were influenza A and 8 were influenza B. Of the 251 influenza A viruses subtyped during Week 40, 242 (96.4%) were influenza A(H1N1)pdm09 and 9 (3.6%) were A(H3N2).
  • Since Week 21, (the week ending May 30, 2026), 79.3% of the influenza A viruses reported have been A(H1N1)pdm09 and among these, the majority have been D.3.1.1 HA subclade.
• Annual seasonal influenza (flu) vaccination is recommended. Influenza vaccines are available for persons aged 6 months and older. For most people, influenza vaccination should ideally be offered during September or October. Influenza vaccination during July and August is not recommended for most groups because of potential waning of immunity over the course of the influenza season.
• There are prescription flu antiviral drugs that can treat flu illness; those should be started as early as possible and are especially important for patients at higher risk for influenza complications .1
• Influenza viruses are among several viruses contributing to respiratory disease activity. CDC is providing updated, integrated information about COVID-19, flu, and respiratory syncytial virus (RSV) activity on a weekly basis.

U.S. Virologic Surveillance​

Nationally, and in HHS Regions 4, 6, 7, 8, and 9, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories increased (change of at least 0.5 percentage points) compared to the previous week. In HHS Regions 1, 2, 3, 5, and 10, the percentage remained stable. Influenza A(H1N1)pdm09 viruses were the most frequently reported by public health laboratories this week. For regional and state level data and age group distribution, please visit FluView Interactive. Viruses known to be associated with recent receipt of live attenuated influenza vaccine (LAIV) 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 virus) are used to monitor whether influenza activity is increasing or decreasing.

	Week 40	Week 39
No. of specimens tested	45,331	53,137
No. of positive specimens (%)	2,270 (5.0%)	2,070 (3.9%)
Positive specimens by type
Influenza A	2,222 (97.9%)	2,011 (97.1%)
Influenza B	48 (2.1%)	59 (2.9%)

Public 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 influenza viruses that belong to each influenza subtype.

	Week 40	Week 39
No. of specimens tested	800	1,210
No. of positive specimens	300	449
Positive specimens by type/subtype
Influenza A	292 (97.3%)	443 (98.7%)
Subtyping performed	251 (86.0%)	374 (84.4%)
(H1N1)pdm09	242 (96.4%)	368 (98.4%)
H3N2	9 (3.6%)	6 (1.6%)
H3N2v†	0	0
H5*	0	0
Subtyping not performed	41 (14.0%)	69 (15.6%)
Influenza B	8 (2.7%)	6 (1.3%)

†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 exposure to swine, but person-to-person 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.

*These data reflect specimens tested, and the number determined to be positive for influenza viruses at the public health labs (specimens tested are not the same as cases). If a specimen is only tested at CDC, it is not reflected in these data. The data could include more than one specimen tested per person. For more information on the number of people infected with A(H5) viruses, please visit "How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation"



This graph reflects the number of specimens determined to be positive for influenza viruses at the public health laboratory (specimens tested are not the same as cases). It does not reflect specimens tested only at CDC and could include more than one specimen tested per person. Specimens tested as part of routine influenza surveillance as well as those tested as part of targeted testing for people exposed to influenza A(H5) are included.

Additional virologic ​

Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data

Novel Influenza A Virus Infections​

No new confirmed human infections with a novel influenza virus were reported to CDC as of October 14, 2026.

Novel influenza A virus infections include human infections with influenza A viruses that are different from currently circulating human seasonal influenza A(H1) and A(H3) viruses or avian influenza A viruses that have sporadically infected people.

An up-to-date summary of confirmed novel influenza virus cases is available at https://gis.cdc.gov/grasp/fluview/Novel_Influenza.html.

Additional information regarding human infections with novel influenza A viruses:​

Surveillance Methods | FluView Interactive

Influenza Virus Characterization​

CDC performs genetic and antigenic characterization of U.S. viruses submitted from state and local public health laboratories according to the Right Size Roadmap submission guidance. These data are used to compare how similar the currently circulating influenza viruses are relative to the reference viruses representing 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 polymerase acidic protein (PA) endonuclease inhibitor baloxavir. The HA clade and subclades were assigned using Nextclade (https://clades.nextstrain.org).

CDC has genetically characterized 416 influenza viruses collected since May 24, 2026.

Virus Subtype or Lineage	Genetic Characterization
Total No. of Subtype/ Lineage Characterized	HA Clade	Number (% of subtype/ lineage Characterized)	HA Subclade	Number (% of subtype/lineage Characterized)
A(H1N1)pdm09	252
		5a.2a.1	252 (100%)	D.3.1	1 (0.4%)
D.3.1.1	251 (99.6%)
A(H3N2)	78
		2a.3a.1	78 (100%)	J.2.4.2	5 (6.4%)
K	73 (93.6%)
B/Victoria	86
		3a.2	86 (100%)	C.3.1	39 (45.3%)
C.3.3	1 (1.2%)
C.5.1	2 (2.3%)
C.5.6	5 (5.8%)
C.5.6.1	39 (45.3%)

Genetic Characterization of Hemagglutinin Genes from Influenza Viruses Collected since May 24, 2026

• A(H1N1)pdm09
• A(H3N2)
• B/Victoria

Genetic characterization of hemagglutinin (HA) genes from influenza A(H1N1)pdm09 viruses collected since May 24, 2026Monthly virus sequence counts and HA subclade proportions
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CDC antigenically characterizes influenza viruses by hemagglutination inhibition (HI) assay (A(H1N1)pdm09, A(H3N2), and B/Victoria viruses) or neutralization-based HINT (H3N2 viruses) using antisera that ferrets make after being infected with reference viruses representing the 2026-2027 Northern Hemisphere recommended cell-, recombinant- and nucleic acid-based influenza vaccine viruses. Antigenic differences between viruses are determined by comparing how well the antibodies made against the vaccine reference viruses recognize the circulating viruses that have been grown in cell culture. Ferret antisera are useful because antibodies raised against a particular virus can often recognize small changes in the surface proteins of other viruses. In HI assays, viruses with similar antigenic properties have antibody titer differences of less than or equal to 4-fold when compared to the reference (vaccine) virus. In HINT, viruses with similar antigenic properties have antibody neutralization titer differences of less than 8-fold. Viruses selected for antigenic characterization are a subset of the recent genetically characterized viruses and are chosen based on the genetic changes in their surface proteins and may not be proportional to the number of such viruses circulating in the United States.

Influenza A Viruses​

• A (H1N1)pdm09: 74 A(H1N1)pdm09 viruses were antigenically characterized by HI, and 70 (94.6%) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown A/Missouri/11/2025-like reference viruses representing the A(H1N1)pdm09 component for the cell-, recombinant- and nucleic acid-based influenza vaccines.
• A (H3N2): 20 A(H3N2) viruses were antigenically characterized by HI or HINT, and 20 (100%) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer in HI or reacting at titers that were less than 8-fold of the homologous virus in HINT) by ferret antisera to cell-grown A/Darwin/1415/2025-like reference viruses representing the A(H3N2) component for the cell-, recombinant- and nucleic acid-based influenza vaccines.

Influenza B Viruses​

• B/Victoria: 30 influenza B/Victoria-lineage viruses were antigenically characterized by HI, and 30 (100%) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown B/Pennsylvania/14/2025-like reference viruses representing the B/Victoria component for the cell-, recombinant- and nucleic acid-based influenza vaccines.

Assessment of Virus Susceptibility to Antiviral Medications​

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 U.S. since May 24, 2026, were tested for antiviral susceptibility as follows:

Antiviral Medication	Total Viruses	A/H1	A/H3	B/Victoria
Neuraminidase Inhibitors
Oseltamivir
Viruses Tested	430	259	86	85
Reduced Inhibition	8 (1.9%)	8 (3.1%)	0	0
Highly Reduced Inhibition	0	0	0	0
Peramivir
Viruses Tested	430	259	86	85
Reduced Inhibition	0	0	0	0
Highly Reduced Inhibition	0	0	0	0
Zanamivir
Viruses Tested	430	259	86	85
Reduced Inhibition	0	0	0	0
Highly Reduced Inhibition	0	0	0	0
PA Cap-Dependent Endonuclease Inhibitor
Baloxavir
Viruses Tested	410	243	81	86
Decreased Susceptibility	0	0	0	0

Eight A(H1N1)pdm09 viruses had amino acid substitutions NA-I223V and NA-S247N and showed reduced inhibition by oseltamivir.

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 and Emergency Department Illness Surveillance​

ILINet​

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient and emergency department visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and can therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms. 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 picture.

Nationally, during Week 40, 2.1% of patient visits reported through ILINet were due to ILI. This week's national percentage increased (change of > 0.1 percentage points) compared to Week 39 and is below the national baseline of 2.9%. ILI activity increased in HHS regions 1, 2, 3, 4, 6, 8, and 9 and remained stable (change of ≤ 0.1 percentage points) in regions 5, 7, and 10 compared to Week 39. All regions are below their respective baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.


*Some calendar years do not include an epidemiologic Week 53. In those years, the Week 53 value shown is the average between Week 52 and Week 1.

**Effective October 3, 2021 (Week 40), the respiratory illness definition (fever plus cough or sore throat) no longer includes "without a known cause other than influenza."

The percentage of visits for respiratory illness increased (change of > 0.1 percentage points) in the 0-4 years and 5-24 years age groups and remained stable (change of ≤ 0.1 percentage points) in the 25-49 years, 50-64 years, and 65 years and older age groups this week compared to the previous week.

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).

Activity Level	Number of Jurisdictions	Number of CBSAs
Week 40 (Week ending Oct. 10, 2026)	Week 39 (Week ending Oct. 3, 2026)	Week 40 (Week ending Oct. 10, 2026)	Week 39 (Week ending Oct. 3, 2026)
Very High	0	0	0	0
High	0	0	3	3
Moderate	1	0	8	6
Low	5	2	53	33
Minimal	49	53	645	656
Insufficient Data	0	0	220	231

*Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of respiratory virus 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

National Syndromic Surveillance System (NSSP)​

The national percentage of emergency department (ED) visits with a discharge diagnosis (DD) of influenza reported in NSSP was 0.8% during Week 40 and increased (change of > 0.1 percentage point) compared to the previous week. Nationally, the percentage of ED visits with a DD of influenza increased among the 0-4 years and 5-17 years age groups and remained stable among the 18-64 years and 65 years and older age groups. The percentage of ED visits with a DD of influenza increased this week compared to the previous week in HHS regions 4, 6, and 9, and remained stable in all other regions (1, 2, 3, 5, 7, 8, and 10). The age group trends varied by region but most regions reported a pattern similar to the national data.

RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season
2026-2027x
2025-2026x
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Age Group​

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Additional information about emergency department visits for flu for current and past seasons:​

Surveillance Methods | Emergency Department Visits for COVID-19, flu, and RSV

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 10% of the U.S. population. FluSurv-NET hospitalization data are preliminary. As data are received each week, prior case counts and rates are updated accordingly.

A total of 256 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 4, 2026, and October 10, 2026. The weekly hospitalization rate observed during Week 40 was 0.7 per 100,000 population. After accounting for reporting delays, the estimated rate during Week 40 was 1.2 per 100,000 population, and weekly rates have continued to increase in recent weeks.

Among all hospitalizations, 247 (96.5%) were associated with influenza A virus and 9 (3.5%) with influenza B virus. Among those with influenza A subtype information, 2 (6.1%) were A(H3N2), and 31 (93.9%) were A(H1N1)pdm09.

When examining rates by age, the highest rate of hospitalization per 100,000 population was among adults aged 65 and older (2.3), followed by adults aged 50-64 years (0.8), children aged 0-4 years (0.6), children aged 5-17 years (0.2), and adults aged 18-49 years (0.2).

Additional FluSurv-NET information for current and past seasons:​

Surveillance Methods | FluView Interactive: Rates by Age, Sex, and Race/Ethnicity or Data on Patient Characteristics

National Healthcare Safety Network (NHSN) Hospital Respiratory Data​

Hospitals report to NHSN the weekly number of patients with laboratory-confirmed influenza who were admitted to the hospital. Nationally, during Week 40, 4,024 laboratory-confirmed influenza-associated hospitalizations were reported. This week's influenza-associated hospital admission rate (1.2 per 100,000 population) remained stable (difference of < 0.2) compared to Week 39.

Laboratory-confirmed influenza-associated hospital admission rates per 100,000 population increased in HHS regions 2, 5, and 6 and remained stable in all other regions this week compared to the previous week. Regional admission rates during Week 40 ranged from 0.5 (Region 7) to 1.5 (Region 4).

When examining rates by age for Week 40, the 0-4 years and 65 years and older age groups increased and all other age groups (5-17 years, 18-49 years, and 50-64 years) remained stable compared to the previous week. The highest hospital admission rate per 100,000 population was among those 65 years and older (3.8), followed by the 0-4 years age group (1.3) and the 50-64 years age group (1.1).

Additional NHSN Hospital Respiratory Data Module information​

Surveillance Methods | Additional Data | FluView Interactive

Mortality Surveillance​

National Center for Health Statistics (NCHS)​

Based on NCHS mortality surveillance data available on October 15, 2026, 0.2% of the deaths that occurred during the week ending October 10, 2026 (Week 40) were due to influenza. This percentage increased (≥ 0.1 percentage point change) compared to Week 39. The data presented are preliminary and may change as more data are received and processed.

Additional mortality surveillance information for current and past seasons (including pneumonia, influenza, and COVID-19):​

Surveillance Methods | FluView Interactive

Influenza-Associated Pediatric Mortality​

No influenza-associated pediatric deaths occurring during the 2026-2027 season have been reported to CDC.

Additional pediatric mortality surveillance information for current and past seasons:​

Surveillance Methods | FluView Interactive

Weekly US Influenza Surveillance Report: Key Updates for Week 40, ending October 10, 2026

Seasonal influenza activity is increasing in many parts of the country but remains low.

www.cdc.gov