sharon sanders
Editor-in-Chief & President
Weekly US Influenza Surveillance Report: Key Updates for Week 4, ending January 31, 2026
For Everyone
Feb. 6, 2026
Key points
Seasonal influenza activity remains elevated nationally.
Summary
Viruses
Clinical Lab 18.0% (Trend
)
positive for influenza
this week. Public Health Lab The most frequently reported
influenza viruses this week were influenza A(H3N2).
Illness
Outpatient Respiratory Illness 4.4% (Trend
)
of visits to a health care provider this week were for respiratory illness
(above baseline). Activity Map 7 moderate jurisdictions 27 high or very high jurisdictions FluSurv-NET 63.2
cumulative hospitalization rate
per 100,000 population NHSN LTCF Respiratory
Data 27.5 (Trend
) weekly hospitalization rate
per 100,000 residents NHSN Hospital Respiratory Data 14,548 (Trend
)
patients admitted to hospitals
with influenza this week. NCHS Mortality 1.2% (Trend
) of deaths attributed to influenza this week. Pediatric Deaths 8 influenza-associated deaths were reported this week for a total of 60 deaths this season.
All data are preliminary and may change as more reports are received.
Directional arrows indicate changes between the current week and the previous week. Additional information on the arrows can be found at the bottom of this page.
A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.[SUP]1[/SUP]
Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.
Key Points
Nationally, the percentage of respiratory specimens testing positive for the influenza virus in clinical laboratories remained stable (change < 0.5 percentage points). The percent positivity for influenza A decreased, while the percent positivity for influenza B has increased for two consecutive weeks. Influenza A(H3N2) viruses were the most frequently reported influenza viruses this week nationally and in all HHS regions. Trends in percent positivity and the distribution of circulating viruses varies by HHS region. 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.
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/lineage.
[SUB]*These data reflect specimens tested, and the number determined to be positive for influenza viruses at the public health labs (specimens tested is not the same as cases). The data do 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"[/SUB]
[SUB][SUP]†[/SUP]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 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 human-to-human.[/SUB]
[SUB]*This graph reflects the number of specimens determined to be positive for influenza viruses at the public health lab (specimens tested is 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 avian influenza A(H5) are included.[/SUB]
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 avian influenza A(H5) virus were reported to CDC this week. To date, person-to-person transmission of avian influenza A(H5) virus (H5 bird flu) has not been identified in the United States.
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 human case summary during the current outbreak 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
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 1,303 influenza viruses collected since September 28, 2025.
CDC antigenically characterizes influenza viruses by hemagglutination inhibition (HI) assay (H1N1pdm09, H3N2, and B/Victoria viruses) or neutralization-based HINT (H3N2 viruses) using antisera from ferrets infected with reference viruses representing the recommended cell-based or recombinant influenza vaccines for the 2025-2026 Northern Hemisphere season. Antigenic differences between viruses are determined by comparing how well the antibodies raised against the vaccine reference viruses recognize the circulating viruses, which were 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 are deemed antigenically similar when their HI titer differences are less than or equal to 4-fold. In HINT, viruses with similar antigenic properties have antibody neutralization titer differences of less than 8-fold. Circulating viruses with antigenic testing results that show titer differences greater than 4-fold by HI or equal to or greater than 8-fold by HINT) are considered “low reactors” or antigenically drifted compared to the vaccine virus. From the recent genetically characterized viruses, a subset is selected for antigenic characterization based on identified genetic changes in their surface proteins. The subset tested may not be proportional to the number of such viruses circulating in the United States.
Influenza A Viruses
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 September 28, 2025, were tested for antiviral susceptibility as follows:
Two A(H1N1)pdm09 viruses had NA-H275Y amino acid substitution conferring highly reduced inhibition by oseltamivir and peramivir. Four A(H1N1)pdm09 viruses had amino acid substitutions NA-I223V and NA-S247N and showed reduced inhibition by oseltamivir. One B virus had amino acid substitution NA- M464T and showed reduced inhibition by peramivir.
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
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 will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza virus, SARS-CoV-2, and RSV. 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 4, 4.4% 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 week’s national percentage decreased (change of > 0.1 percentage points) slightly but remains above the national baseline for the ninth consecutive week. ILI activity increased (change of > 0.1 percentage points) in HHS Region 10, decreased (change of > 0.1 percentage points) in regions 1, 2, 3, 5, and 6, and remained stable (change of ≤ 0.1 percentage points) in regions 4, 7, 8, and 9 this week compared to Week 3. Region 2 is below its regional baseline for the second consecutive week while all other regions (1, 3, 4, 5, 6, 7, 8, 9, and 10) remain above their respective baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.
[SUB]*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.[/SUB]
[SUB]**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."[/SUB]
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 decreased (change of > 0.1 percentage points) in the 0-4 years age group and remained stable (change of ≤ 0.1 percentage points) in all other age groups (5-24 years, 25-49 years, 50-64 years, and 65 years and older) this week compared to Week 3.
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).
[SUB]*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.[/SUB]
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 3.3% during Week 4 which is stable (change of ≤ 0.1 percentage point) compared to the previous week. Nationally, the percentage of ED visits with a DD of influenza remained stable among the 18-64 years age group and decreased (change of > 0.1 percentage points) among all other age groups (0-4 years, 5-17 years, and 65 years and older). The percentage of ED visits with a DD of influenza increased this week compared to the previous week in HHS Region 10, remained stable in regions 4 and 9, and decreased in all other regions (1, 2, 3, 5, 6, 7, and 8). Age group trends varied by region. RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season
2025-2026x
2024-2025x
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2.0%4.0%6.0%8.0%10.0%12.0%14.0%16.0%18.0%20.0%Perc ent of Emergency Department Visits for InfluenzaWeek 41 of 2024Week 45 of 2024Week 49 of 2024Week 1 of 2025Week 5 of 2025Week 9 of 2025Week 13 of 2025Week 17 of 2025Week 21 of 2025Week 25 of 2025Week 29 of 2025Week 33 of 2025Week 37 of 2025Week 41 of 2025Week 45 of 2025Week 49 of 2025Week 53 of 2025Week 4 of 2026
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 22,045 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1, 2025, and January 31, 2026. The weekly hospitalization rate observed during Week 4 was 2.2 per 100,000 population, which decreased from last week. After accounting for reporting delays, the estimated rate during Week 4 likely ranges from 2.9 to 3.8. The cumulative hospitalization rate observed in Week 4 was 63.2 per 100,000 population and is the highest cumulative rate this week since the 2010-11 season.
Among all hospitalizations, 21,286 (96.6%) were associated with influenza A virus, 627 (2.8%) with influenza B virus, 25 (0.1%) with influenza A virus and influenza B virus co-infection, and 107 (0.5%) with influenza virus for which the type was not determined. Among those with influenza A subtype information, 4,976 (90.9%) were A(H3N2), and 498 (9.1%) 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 (211.9), followed by children aged 0-4 years (66.1), adults aged 50-64 years (55.8), adults aged 18-49 years (24.4), and children aged 5-17 years (24.3).
Among children, the peak weekly rate is the highest going back to the 2010-11 season in Week 52 (7.1). The cumulative rate for pediatric cases is the second highest since 2010-11 (35.0). Among children, rates are highest among infants aged less than 1 year (105.6), followed by children aged 1-4 years (56.4). For all pediatric age groups, this is the second highest cumulative rate at this time of the season since the 2010-11 season.
When examining age-adjusted rates by race and ethnicity, the highest rate of hospitalization per 100,000 population was among non-Hispanic Black persons (113.7), followed by American Indian or Alaska Native persons (61.8), Hispanic persons (57.3), non-Hispanic White persons (54.2), and Asian and/or Pacific Islander persons (27.3).
Among 1,840 hospitalized adults with information on underlying medical conditions, 96.8% had at least one reported underlying medical condition; the most commonly reported were hypertension, cardiovascular disease, chronic metabolic disease, and chronic lung disease. Among 2,508 hospitalized women of childbearing age (15-49 years) with information on pregnancy status, 31.9% were pregnant. Among 752 hospitalized children with information on underlying medical conditions, 72.8% had at least one reported underlying medical condition; the most commonly reported was asthma, followed by neurologic disorder, and obesity.
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 https://www.cdc.gov/flu-burden/php/data-vis/index.html. View LargerDownload
[SUB]**In this figure, weekly rates for all seasons prior to the 2025-26 season reflect end-of-season rates. For the 2025-26 season, rates for recent hospital admissions are subject to reporting delays and are shown as a dashed line for the current season. As hospitalization data are received each week, prior case counts and rates are updated accordingly.[/SUB] 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 4, 14,548 laboratory-confirmed influenza-associated hospitalizations were reported. This week's influenza-associated hospital admission rate (4.3 per 100,000 population) decreased (difference of < 0.2) compared to Week 3.
Laboratory confirmed influenza-associated hospital admission rates per 100,000 population decreased in HHS regions 1, 2, 3, 5, 6, 7, and 8, increased in Region 10, and remained stable in regions 4 and 9. Region admission rates ranged from 2.7 (Region 2) to 6.4 (Region 7) during Week 4.
When examining rates by age for Week 4, all age groups decreased. The highest hospital admission rate per 100,000 population was among those 65 years and older (13.7), followed by the 0-4 years age group (4.5), and the 50-64 years age group (3.6).
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.
Nationally, during Week 4, the hospitalization rate for residents with a positive influenza test in the prior 10 days was 27.5 per 100,000 residents. The national rate and rates in HHS regions 1, 2, 3, 4, 5, 7, and 8 are trending downward. Rates continue to increase in Region 10. The rates do not show a consistent trend in regions 6 and 9. View LargerDownload
National Healthcare Safety Network (NHSN) Long-Term Care Respiratory Pathogens & Vaccination Module
Mortality surveillance
National Center for Health Statistics (NCHS) Mortality Surveillance
Based on NCHS mortality surveillance data available on February 5, 2026, 1.2% of the deaths that occurred during the week ending January 31, 2026 (Week 4), were due to influenza. This percentage decreased (≥ 0.1 percentage point change) compared to Week 3. 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
Eight influenza-associated pediatric deaths occurring during the 2025-2026 season were reported to CDC during Week 4. The deaths occurred during weeks 51, 52, 1 and 3 (the weeks ending December 20, 2025, December 27, 2025, January 10, 2026, and January 24, 2026). All eight deaths were associated with influenza A viruses. Six of the influenza A viruses had subtyping performed and all were A(H3N2) viruses.
A total of 60 influenza-associated pediatric deaths occurring during the 2025–2026 season have been reported to CDC. Among children who were eligible for influenza vaccination and with known vaccination status, approximately 90% of reported pediatric deaths this season have occurred in children who were not fully vaccinated against influenza.
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.[SUP]1[/SUP]
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
Indicators Status by System
Increasing:
Decreasing:
Stable:
Clinical Labs: Up or down arrows indicate a change of greater than or equal to 0.5 percentage points in the percent of specimens positive for influenza compared to the previous week.
Outpatient Respiratory Illness (ILINet): Up or down arrows indicate a change of greater than 0.1 percentage points in the percent of visits due to respiratory illness (ILI) compared to the previous week.
NHSN Hospitalizations: Up or down arrows indicate change of greater than or equal to 0.2 in the rate of hospital admissions or greater than or equal to 691 patients admitted with laboratory-confirmed influenza compared to the previous week.
NHSN Long- Term Care (LTC): Up or down arrows indicate change of greater than or equal to 5% in hospitalization rates for residents in LTC facilities who were hospitalized with laboratory-confirmed influenza compared to the previous week.
NCHS Mortality: Up or down arrows indicate change of greater than 0.1 percentage points of the percent of deaths due to influenza compared to the previous week.
Additional 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.
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.
https://www.cdc.gov/fluview/surveillance/2026-week-04.html
For Everyone
Feb. 6, 2026
Key points
Seasonal influenza activity remains elevated nationally.
Summary
Viruses
Clinical Lab 18.0% (Trend
positive for influenza
this week. Public Health Lab The most frequently reported
influenza viruses this week were influenza A(H3N2).
Illness
Outpatient Respiratory Illness 4.4% (Trend
of visits to a health care provider this week were for respiratory illness
(above baseline). Activity Map 7 moderate jurisdictions 27 high or very high jurisdictions FluSurv-NET 63.2
cumulative hospitalization rate
per 100,000 population NHSN LTCF Respiratory
Data 27.5 (Trend
per 100,000 residents NHSN Hospital Respiratory Data 14,548 (Trend
patients admitted to hospitals
with influenza this week. NCHS Mortality 1.2% (Trend
All data are preliminary and may change as more reports are received.
Directional arrows indicate changes between the current week and the previous week. Additional information on the arrows can be found at the bottom of this page.
A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.[SUP]1[/SUP]
Additional information on the current and previous influenza seasons for each surveillance component are available on FluView Interactive.
Key Points
- Seasonal influenza activity remains elevated nationally. Most areas of the country are reporting stable or decreasing trends in activity; however, activity continues to increase in HHS Region 10 (Pacific Northwest).
- Influenza A activity is decreasing while influenza B activity is increasing nationally and in most areas of the country; however, trends vary by region.
- Influenza A(H3N2) viruses are the most frequently reported influenza viruses so far this season.
- Among 822 influenza A(H3N2) viruses collected since September 28, 2025, that underwent additional genetic characterization at CDC, 91.5% belonged to subclade K.
- The weekly influenza-associated hospitalization rate overall in FluSurv-Net peaked during Week 52 at 12.8 per 100,000 population. This is the second highest peak weekly rate overall since the 2010-2011 season. Notably, children younger than 18 years have the highest peak weekly hospitalization rate observed since the 2010-2011 season.
- Eight influenza-associated pediatric deaths occurring in the 2025-2026 season were reported to CDC this week, bringing the season total to 60 reported influenza-associated pediatric deaths.
- Among children who were eligible for influenza vaccination and with known vaccination status, approximately 90% of reported pediatric deaths this season have occurred in children who were not fully vaccinated against influenza.
- CDC's in-season severity assessment framework classified the season as moderate across all ages. CDC also assesses severity by three age groups: pediatric (0-17 years), adult (18-64 years), and older adults (≥65 years). At this point in the season, the pediatric age group is classified as having high severity, while both the adult and older adult age groups are classified as having moderate severity. These assessments are conducted each week during the season, and the season's severity assessment can change if activity should increase again.
- CDC estimates that there have been at least 22,000,000 illnesses, 280,000 hospitalizations, and 12,000 deaths from flu so far this season.
- Influenza (flu) vaccination has been shown to reduce the risk of flu and its potentially serious complications. There is still time to get vaccinated against flu this season. Approximately 134 million doses of influenza vaccine have been distributed in the United States this 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 flu-related complications.[SUP]1[/SUP]
- Influenza viruses are among several viruses contributing to respiratory disease activity. CDC provides updated, integrated information about COVID-19, flu, and respiratory syncytial virus (RSV) activity on a weekly basis.
- No new avian influenza A(H5) infections were reported to CDC this week. To date, person-to-person transmission of influenza A(H5) viruses has not been identified in the United States.
Nationally, the percentage of respiratory specimens testing positive for the influenza virus in clinical laboratories remained stable (change < 0.5 percentage points). The percent positivity for influenza A decreased, while the percent positivity for influenza B has increased for two consecutive weeks. Influenza A(H3N2) viruses were the most frequently reported influenza viruses this week nationally and in all HHS regions. Trends in percent positivity and the distribution of circulating viruses varies by HHS region. 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.
| No. of specimens tested | 71,514 | 1,385,003 |
| No. of positive specimens (%) | 12,869 (18.0%) | 190,020 (13.7%) |
| Positive specimens by type | ||
| Influenza A | 9,893 (76.9%) | 174,848 (92.0%) |
| Influenza B | 2,976 (23.1%) | 15,172 (8.0%) |
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/lineage.
| No. of specimens tested | 1,527 | 50,378 |
| No. of positive specimens | 1,102 | 33,908 |
| Positive specimens by type/subtype | ||
| Influenza A | 1,023 (92.8%) | 32,669 (96.3%) |
| Subtyping Performed | 775 (75.8%) | 27,314 (83.6%) |
| (H1N1)pdm09 | 111 (14.3%) | 3,163 (11.6%) |
| H3N2 | 664 (85.7%) | 24,149 (88.4%) |
| H3N2v[SUP]†[/SUP] | 0 | 0 |
| H5* | 0 | 2 (<0.1%) |
| Subtyping not performed | 248 (24.2%) | 5,355 (16.4%) |
| Influenza B | 79 (7.2%) | 1,239 (3.7%) |
| Lineage testing performed | 28 (35.4%) | 376 (30.3%) |
| Yamagata lineage | 0 | 0 |
| Victoria lineage | 28 (100%) | 376 (100%) |
| Lineage not performed | 51 (64.6%) | 863 (69.7%) |
[SUB][SUP]†[/SUP]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 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 human-to-human.[/SUB]
[SUB]*This graph reflects the number of specimens determined to be positive for influenza viruses at the public health lab (specimens tested is 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 avian influenza A(H5) are included.[/SUB]
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 avian influenza A(H5) virus were reported to CDC this week. To date, person-to-person transmission of avian influenza A(H5) virus (H5 bird flu) has not been identified in the United States.
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 human case summary during the current outbreak 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
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 1,303 influenza viruses collected since September 28, 2025.
| A/H1 | 349 | ||||
| 5a.2a | 2 (0.6%) | C.1.9.3 | 2 (0.6%) | ||
| 5a.2a.1 | 347 (99.4%) | D.3.1 | 155 (44.4%) | ||
| D.3.1.1 | 192 (55.0%) | ||||
| A/H3 | 822 | ||||
| 2a.3a.1 | 822 (100%) | J.2 | 4 (0.5%) | ||
| J.2.2 | 5 (0.6%) | ||||
| J.2.3 | 28 (3.4%) | ||||
| J.2.4 | 33 (4.0%) | ||||
| K | 752 (91.5%) | ||||
| B/Victoria | 132 | ||||
| 3a.2 | 132 (100%) | C.3 | 3 (2.3%) | ||
| C.3.1 | 80 (60.6%) | ||||
| C.5.1 | 15 (11.4%) | ||||
| C.5.6 | 10 (7.6%) | ||||
| C.5.6.1 | 11 (8.3%) | ||||
| C.5.7 | 13 (9.8%) | ||||
| B/Yamagata | 0 | ||||
| Y3 | 0 | Y3 | 0 |
Influenza A Viruses
- A(H1N1)pdm09: 95 A(H1N1)pdm09 viruses collected since September 28, 2025, were antigenically characterized by HI, and 93 (97.9%) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown A/Wisconsin/67/2022-like reference viruses representing the A(H1N1)pdm09 component for the cell- and recombinant-based influenza vaccines.
- A(H3N2): 99 A(H3N2) viruses collected since September 28, 2025, were antigenically characterized by HI or HINT, and 4 (4.0%) 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/District Of Columbia/27/2023-like reference viruses representing the A(H3N2) component for the cell- and recombinant-based influenza vaccines.
- B/Victoria: 31 influenza B/Victoria-lineage viruses collected since September 28, 2025, since were antigenically characterized by HI, and 16 (51.6%) were well-recognized (reacting at titers that were within 4-fold of the homologous virus titer) by ferret antisera to cell-grown B/Austria/1359417/2021-like reference viruses representing the B/Victoria component for the cell- and recombinant-based influenza vaccines.
- B/Yamagata: No influenza B/Yamagata-lineage viruses were available for antigenic characterization.
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 September 28, 2025, were tested for antiviral susceptibility as follows:
| Neuraminidase Inhibitors | Oseltamivir | Viruses Tested | 1,291 | 351 | 811 | 129 |
| Reduced Inhibition | 4 (0.3%) | 4 (1.1%) | 0 | 0 | ||
| Highly Reduced Inhibition | 2 (0.2%) | 2 (0.6%) | 0 | 0 | ||
| Peramivir | Viruses Tested | 1,291 | 351 | 811 | 129 | |
| Reduced Inhibition | 1 (0.1%) | 0 | 0 | 1 (0.8%) | ||
| Highly Reduced Inhibition | 2 (0.2%) | 2 (0.6%) | 0 | 0 | ||
| Zanamivir | Viruses Tested | 1,291 | 351 | 811 | 129 | |
| Reduced Inhibition | 0 | 0 | 0 | 0 | ||
| Highly Reduced Inhibition | 0 | 0 | 0 | 0 | ||
| PA Cap-Dependent Endonuclease Inhibitor | Baloxavir | Viruses Tested | 1,249 | 328 | 794 | 127 |
| Decreased Susceptibility | 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 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 will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza virus, SARS-CoV-2, and RSV. 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 4, 4.4% 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 week’s national percentage decreased (change of > 0.1 percentage points) slightly but remains above the national baseline for the ninth consecutive week. ILI activity increased (change of > 0.1 percentage points) in HHS Region 10, decreased (change of > 0.1 percentage points) in regions 1, 2, 3, 5, and 6, and remained stable (change of ≤ 0.1 percentage points) in regions 4, 7, 8, and 9 this week compared to Week 3. Region 2 is below its regional baseline for the second consecutive week while all other regions (1, 3, 4, 5, 6, 7, 8, 9, and 10) remain above their respective baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.
[SUB]*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.[/SUB]
[SUB]**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."[/SUB]
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 decreased (change of > 0.1 percentage points) in the 0-4 years age group and remained stable (change of ≤ 0.1 percentage points) in all other age groups (5-24 years, 25-49 years, 50-64 years, and 65 years and older) this week compared to Week 3.
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 4 (Week ending Jan. 31, 2026) | Week 3 (Week ending Jan. 24, 2026) | Week 4 (Week ending Jan. 31, 2026) | Week 3 (Week ending Jan. 24, 2026) | |
| Very High | 7 | 6 | 26 | 23 |
| High | 20 | 24 | 122 | 125 |
| Moderate | 7 | 10 | 150 | 158 |
| Low | 12 | 8 | 208 | 217 |
| Minimal | 9 | 7 | 201 | 183 |
| Insufficient Data | 0 | 0 | 222 | 223 |
[SUB]*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.[/SUB]
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 3.3% during Week 4 which is stable (change of ≤ 0.1 percentage point) compared to the previous week. Nationally, the percentage of ED visits with a DD of influenza remained stable among the 18-64 years age group and decreased (change of > 0.1 percentage points) among all other age groups (0-4 years, 5-17 years, and 65 years and older). The percentage of ED visits with a DD of influenza increased this week compared to the previous week in HHS Region 10, remained stable in regions 4 and 9, and decreased in all other regions (1, 2, 3, 5, 6, 7, and 8). Age group trends varied by region. RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season
2025-2026x
2024-2025x
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2.0%4.0%6.0%8.0%10.0%12.0%14.0%16.0%18.0%20.0%Perc ent of Emergency Department Visits for InfluenzaWeek 41 of 2024Week 45 of 2024Week 49 of 2024Week 1 of 2025Week 5 of 2025Week 9 of 2025Week 13 of 2025Week 17 of 2025Week 21 of 2025Week 25 of 2025Week 29 of 2025Week 33 of 2025Week 37 of 2025Week 41 of 2025Week 45 of 2025Week 49 of 2025Week 53 of 2025Week 4 of 2026
Age Group
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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 22,045 laboratory-confirmed influenza-associated hospitalizations were reported by FluSurv-NET sites between October 1, 2025, and January 31, 2026. The weekly hospitalization rate observed during Week 4 was 2.2 per 100,000 population, which decreased from last week. After accounting for reporting delays, the estimated rate during Week 4 likely ranges from 2.9 to 3.8. The cumulative hospitalization rate observed in Week 4 was 63.2 per 100,000 population and is the highest cumulative rate this week since the 2010-11 season.
Among all hospitalizations, 21,286 (96.6%) were associated with influenza A virus, 627 (2.8%) with influenza B virus, 25 (0.1%) with influenza A virus and influenza B virus co-infection, and 107 (0.5%) with influenza virus for which the type was not determined. Among those with influenza A subtype information, 4,976 (90.9%) were A(H3N2), and 498 (9.1%) 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 (211.9), followed by children aged 0-4 years (66.1), adults aged 50-64 years (55.8), adults aged 18-49 years (24.4), and children aged 5-17 years (24.3).
Among children, the peak weekly rate is the highest going back to the 2010-11 season in Week 52 (7.1). The cumulative rate for pediatric cases is the second highest since 2010-11 (35.0). Among children, rates are highest among infants aged less than 1 year (105.6), followed by children aged 1-4 years (56.4). For all pediatric age groups, this is the second highest cumulative rate at this time of the season since the 2010-11 season.
When examining age-adjusted rates by race and ethnicity, the highest rate of hospitalization per 100,000 population was among non-Hispanic Black persons (113.7), followed by American Indian or Alaska Native persons (61.8), Hispanic persons (57.3), non-Hispanic White persons (54.2), and Asian and/or Pacific Islander persons (27.3).
Among 1,840 hospitalized adults with information on underlying medical conditions, 96.8% had at least one reported underlying medical condition; the most commonly reported were hypertension, cardiovascular disease, chronic metabolic disease, and chronic lung disease. Among 2,508 hospitalized women of childbearing age (15-49 years) with information on pregnancy status, 31.9% were pregnant. Among 752 hospitalized children with information on underlying medical conditions, 72.8% had at least one reported underlying medical condition; the most commonly reported was asthma, followed by neurologic disorder, and obesity.
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 https://www.cdc.gov/flu-burden/php/data-vis/index.html. View LargerDownload
[SUB]**In this figure, weekly rates for all seasons prior to the 2025-26 season reflect end-of-season rates. For the 2025-26 season, rates for recent hospital admissions are subject to reporting delays and are shown as a dashed line for the current season. As hospitalization data are received each week, prior case counts and rates are updated accordingly.[/SUB] 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 4, 14,548 laboratory-confirmed influenza-associated hospitalizations were reported. This week's influenza-associated hospital admission rate (4.3 per 100,000 population) decreased (difference of < 0.2) compared to Week 3.
Laboratory confirmed influenza-associated hospital admission rates per 100,000 population decreased in HHS regions 1, 2, 3, 5, 6, 7, and 8, increased in Region 10, and remained stable in regions 4 and 9. Region admission rates ranged from 2.7 (Region 2) to 6.4 (Region 7) during Week 4.
When examining rates by age for Week 4, all age groups decreased. The highest hospital admission rate per 100,000 population was among those 65 years and older (13.7), followed by the 0-4 years age group (4.5), and the 50-64 years age group (3.6).
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.
Nationally, during Week 4, the hospitalization rate for residents with a positive influenza test in the prior 10 days was 27.5 per 100,000 residents. The national rate and rates in HHS regions 1, 2, 3, 4, 5, 7, and 8 are trending downward. Rates continue to increase in Region 10. The rates do not show a consistent trend in regions 6 and 9. View LargerDownload
Mortality surveillance
National Center for Health Statistics (NCHS) Mortality Surveillance
Based on NCHS mortality surveillance data available on February 5, 2026, 1.2% of the deaths that occurred during the week ending January 31, 2026 (Week 4), were due to influenza. This percentage decreased (≥ 0.1 percentage point change) compared to Week 3. 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
Eight influenza-associated pediatric deaths occurring during the 2025-2026 season were reported to CDC during Week 4. The deaths occurred during weeks 51, 52, 1 and 3 (the weeks ending December 20, 2025, December 27, 2025, January 10, 2026, and January 24, 2026). All eight deaths were associated with influenza A viruses. Six of the influenza A viruses had subtyping performed and all were A(H3N2) viruses.
A total of 60 influenza-associated pediatric deaths occurring during the 2025–2026 season have been reported to CDC. Among children who were eligible for influenza vaccination and with known vaccination status, approximately 90% of reported pediatric deaths this season have occurred in children who were not fully vaccinated against influenza.
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.[SUP]1[/SUP]
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
Indicators Status by System
Increasing:
Decreasing:
Stable:
Clinical Labs: Up or down arrows indicate a change of greater than or equal to 0.5 percentage points in the percent of specimens positive for influenza compared to the previous week.
Outpatient Respiratory Illness (ILINet): Up or down arrows indicate a change of greater than 0.1 percentage points in the percent of visits due to respiratory illness (ILI) compared to the previous week.
NHSN Hospitalizations: Up or down arrows indicate change of greater than or equal to 0.2 in the rate of hospital admissions or greater than or equal to 691 patients admitted with laboratory-confirmed influenza compared to the previous week.
NHSN Long- Term Care (LTC): Up or down arrows indicate change of greater than or equal to 5% in hospitalization rates for residents in LTC facilities who were hospitalized with laboratory-confirmed influenza compared to the previous week.
NCHS Mortality: Up or down arrows indicate change of greater than 0.1 percentage points of the percent of deaths due to influenza compared to the previous week.
Additional 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.
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.
https://www.cdc.gov/fluview/surveillance/2026-week-04.html
