Weekly US Influenza Surveillance Report: Key Updates for Week 38, ending September 26, 2026
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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%) |
†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 DataNovel 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 InteractiveOutpatient 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 MapNational 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
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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 RSVHospitalization 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 InteractiveNational 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 InteractiveNational 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 InteractiveInfluenza-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 InteractiveAll 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
