Weekly US Influenza Surveillance Report: Key Updates for Week 35, ending August 30, 2025
For Everyone
Sept. 5, 2025
Key points
Seasonal influenza activity is low.
U.S. virologic surveillance
Clinical Laboratories
The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing. Nationally, during Week 35, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories was 0.4%.
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.
[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. The guidance for avian influenza A(H5) virus testing recommends testing both a conjunctival and respiratory swab for people with conjunctivitis which has resulted in more specimens testing positive for avian influenza A(H5) virus than the number of human A(H5) cases. For more information on the number of people infected with avian influenza 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 tested and the number 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 confirmed human infections with influenza A(H5) virus were reported to CDC this week. To date, human-to-human 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.
The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/h5n1-hpai#detections-hpai.
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 35, 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. Multiple respiratory viruses are co-circulating, and the current relative contribution of influenza virus infection to ILI varies by location. Although ILI activity is rising, other surveillance indicators show this increase is not attributable to influenza, but other respiratory illness pathogens.
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 35, the percentage of visits for respiratory illness reported in ILINet was 5.0% among those 0-4 years, 2.8% among those 5-24 years, 1.5% among those 25-49 years, 0.9% among those 50-64 years, and 0.7% 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).
[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 overall percentage of emergency department (ED) visits with a discharge diagnosis of influenza reported in NSSP was 0.1% during Week 35. The percentage of visits was 0.4% among those 0-4 years, 0.3% among those 5-17 years, and 0.1% among those 18-64 years and 65 years and older. RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season2023-2024 & 2024-20252022-2023 Skip Over Chart Container
2.0%4.0%6.0%8.0%10.0%12.0%14.0%16.0%Percent of Emergency Department Visits for InfluenzaWeek 43 of 2023Week 47 of 2023Week 51 of 2023Week 3 of 2024Week 7 of 2024Week 11 of 2024Week 15 of 2024Week 19 of 2024Week 23 of 2024Week 27 of 2024Week 31 of 2024Week 35 of 2024Week 39 of 2024Week 43 of 2024Week 47 of 2024Week 51 of 2024Week 3 of 2025Week 7 of 2025Week 11 of 2025Week 15 of 2025Week 19 of 2025Week 23 of 2025Week 27 of 2025Week 31 of 2025Week 35 of 2025
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
The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET hospitalization data are preliminary. Patients admitted for laboratory-confirmed influenza-related hospitalization after April 30, 2025, will not be included in FluSurv-NET for the 2024-2025 season. Data on patients admitted through April 30, 2025, will continue to be updated on FluView Interactive as additional information is received.
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 35, 812 (0.2 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 and older (0.8), followed by those 0-4 years (0.3), and 50-64 years (0.2).
Additional NHSN Hospital Respiratory Data information:
Surveillance Methods | Additional Data | FluView Interactive
Mortality surveillance
National Center for Health Statistics (NCHS) Mortality Surveillance
Based on NCHS mortality surveillance data available on September 4, 2025, 0.02% of the deaths that occurred during the week ending August 30, 2025 (Week 35) 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
One influenza-associated pediatric death that occurred during Week 34 (the week ending August 23, 2025) of the 2024-2025 season was reported to CDC during Week 35. A total of 279 influenza-associated pediatric deaths occurring during the 2024-2025 season have been reported to CDC. This is the highest number of pediatric deaths reported in any non-pandemic influenza season since the condition became reportable in 2004.
Among children who were eligible for influenza vaccination and with known vaccine status, 90% of reported pediatric deaths this season (compared to 82% during the 2023-2024 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
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.
https://www.cdc.gov/fluview/surveillance/2025-week-35.html
For Everyone
Sept. 5, 2025
Key points
Seasonal influenza activity is low.
U.S. virologic surveillance
Clinical Laboratories
The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing. Nationally, during Week 35, the percentage of respiratory specimens testing positive for influenza virus in clinical laboratories was 0.4%.
| No. of specimens tested | 39,531 | 3,978,954 |
| No. of positive specimens (%) | 163 (0.4%) | 489,579 (12.3%) |
| Positive specimens by type | ||
| Influenza A | 130 (79.8%) | 434,985 (88.8%) |
| Influenza B | 33 (20.2%) | 54,594 (11.2%) |
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.
| No. of specimens tested | 328 | 155,297 |
| No. of positive specimens | 22 | 100,015 |
| Positive specimens by type/subtype | ||
| Influenza A | 22 (100%) | 94,078 (94.1%) |
| Subtyping Performed | 18 (81.8%) | 84,339 (89.6%) |
| (H1N1)pdm09 | 13 (72.2%) | 44,733 (53.0%) |
| H3N2 | 5 (27.8%) | 39,527 (46.9%) |
| H3N2v[SUP]†[/SUP] | 0 | 0 |
| H5* | 0 | 79 (0.1%) |
| Subtyping not performed | 4 (18.2%) | 9,739 (10.4%) |
| Influenza B | 0 | 5,937 (5.9%) |
| Lineage testing performed | 0 | 3,297 (55.5%) |
| Yamagata lineage | 0 | 0 |
| Victoria lineage | 0 | 3,297 (100%) |
| Lineage not performed | 0 | 2,640 (44.5%) |
[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 tested and the number 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 confirmed human infections with influenza A(H5) virus were reported to CDC this week. To date, human-to-human 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.
The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/h5n1-hpai#detections-hpai.
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 35, 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. Multiple respiratory viruses are co-circulating, and the current relative contribution of influenza virus infection to ILI varies by location. Although ILI activity is rising, other surveillance indicators show this increase is not attributable to influenza, but other respiratory illness pathogens.
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 35, the percentage of visits for respiratory illness reported in ILINet was 5.0% among those 0-4 years, 2.8% among those 5-24 years, 1.5% among those 25-49 years, 0.9% among those 50-64 years, and 0.7% 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 35 (Week ending Aug. 30, 2025) | Week 34 (Week ending Aug. 23, 2025) | Week 35 (Week ending Aug. 30, 2025) | Week 34 (Week ending Aug. 23, 2025) | |
| Very High | 0 | 0 | 0 | 0 |
| High | 0 | 0 | 4 | 1 |
| Moderate | 0 | 0 | 7 | 6 |
| Low | 2 | 0 | 42 | 22 |
| Minimal | 51 | 55 | 590 | 656 |
| Insufficient Data | 2 | 0 | 286 | 244 |
[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 overall percentage of emergency department (ED) visits with a discharge diagnosis of influenza reported in NSSP was 0.1% during Week 35. The percentage of visits was 0.4% among those 0-4 years, 0.3% among those 5-17 years, and 0.1% among those 18-64 years and 65 years and older. RegionNationalRegion 1Region 2Region 3Region 4Region 5Region 6Region 7Region 8Region 9Region 10
Season2023-2024 & 2024-20252022-2023 Skip Over Chart Container
2.0%4.0%6.0%8.0%10.0%12.0%14.0%16.0%Percent of Emergency Department Visits for InfluenzaWeek 43 of 2023Week 47 of 2023Week 51 of 2023Week 3 of 2024Week 7 of 2024Week 11 of 2024Week 15 of 2024Week 19 of 2024Week 23 of 2024Week 27 of 2024Week 31 of 2024Week 35 of 2024Week 39 of 2024Week 43 of 2024Week 47 of 2024Week 51 of 2024Week 3 of 2025Week 7 of 2025Week 11 of 2025Week 15 of 2025Week 19 of 2025Week 23 of 2025Week 27 of 2025Week 31 of 2025Week 35 of 2025
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
The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 14 states and represents approximately 9% of the U.S. population. FluSurv-NET hospitalization data are preliminary. Patients admitted for laboratory-confirmed influenza-related hospitalization after April 30, 2025, will not be included in FluSurv-NET for the 2024-2025 season. Data on patients admitted through April 30, 2025, will continue to be updated on FluView Interactive as additional information is received.
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 35, 812 (0.2 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 and older (0.8), followed by those 0-4 years (0.3), and 50-64 years (0.2).
Additional NHSN Hospital Respiratory Data information:
Surveillance Methods | Additional Data | FluView Interactive
Mortality surveillance
National Center for Health Statistics (NCHS) Mortality Surveillance
Based on NCHS mortality surveillance data available on September 4, 2025, 0.02% of the deaths that occurred during the week ending August 30, 2025 (Week 35) 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
One influenza-associated pediatric death that occurred during Week 34 (the week ending August 23, 2025) of the 2024-2025 season was reported to CDC during Week 35. A total of 279 influenza-associated pediatric deaths occurring during the 2024-2025 season have been reported to CDC. This is the highest number of pediatric deaths reported in any non-pandemic influenza season since the condition became reportable in 2004.
Among children who were eligible for influenza vaccination and with known vaccine status, 90% of reported pediatric deaths this season (compared to 82% during the 2023-2024 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
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.
https://www.cdc.gov/fluview/surveillance/2025-week-35.html