Influenza Activity in the U.S.
Key Points: • During Week 19, of the 501 viruses reported by public health laboratories, 334 were influenza A and 167 were influenza B. Of the 327 influenza A viruses subtyped during Week 19, 195 (59.6%) were influenza A(H1N1)pdm09, 132 (40.4%) were A(H3N2), and 0 were A(H5). • No new influenza A(H5) cases 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. • CDC estimates that there have been at least 47 million illnesses, 610,000 hospitalizations, and 27,000 deaths from flu so far this season. • CDC continues to recommend that everyone ages 6 months and older get an annual flu vaccine as long as influenza viruses are circulating. • 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 severe illness. • 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. Below is a summary of the key influenza indicators for the week ending May 10, 2025: Viral Surveillance - Clinical Lab: The percentage of respiratory specimens testing positive for influenza at clinical laboratories is 2.9% this week. Viral Surveillance - Public Health Lab: Influenza A(H1N1)pdm09, A(H3N2) and B viruses were co-circulating this week. Virus Characterization: Influenza virus characterization information can be found here: Influenza Virus Genome Sequencing and Genetic Characterization Outpatient Illness: The percentage of patient visits to a health care provider for respiratory illness in week 19 was 1.9% which is below baseline. Outpatient Respiratory Illness: ILINet Activity Map: No jurisdictions experienced moderate ILI activity and no jurisdiction experienced high or very high ILI activity in week 19. Laboratory-Confirmed influenza Hospitalizations can be found here: Laboratory-Confirmed Influenza Hospitalizations (cdc.gov) The cumulative hospitalization rate for week 19 was 128.0 per 100,000 population which is the highest cumulative hospitalization rate for all seasons since 2010-2011. NCHS Mortality: 0.2% of deaths were due to influenza in week 19. This percentage remained stable (< 0.1 percentage point change) compared to week 18. (NCHS:National Center for Health Statistics) Influenza-Associated Pediatric Deaths: One influenza-associated death was reported this week. Two hundred and twenty seven pediatric deaths have been reported so far this season. Among children who were eligible for influenza vaccination and with known vaccine status, 90% of reported pediatric deaths have occurred in children who were not fully vaccinated against influenza. For more information: https://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html CDC FluView Site https://www.cdc.gov/fluview/
Influenza Activity in Massachusetts For more information about flu, please go to our Viral Respiratory Disease Dashboard which includes information not only on influenza but also other acute respiratory diseases, COVID-19, and respiratory syncytial virus (RSV), wastewater data and immunizations for respiratory diseases.
The figure below shows that for MMWR week 19 the percent of ILI visits in the current week is below the regional baseline of 1.9%. (The CDC uses trends from past years to determine a region-specific baseline rate of ILI visits, which for Massachusetts is 1.9%. A rate above this regional baseline indicates higher than normal levels of ILI in the state.) For more information on how regional baselines are calculated see CDC’s influenza surveillance website at U.S. Influenza Surveillance: Purpose and Methods | FluView | CDC) For more information on weekly flu activity, see CDC’s influenza surveillance website at https://www.cdc.gov/fluview/surveillance/index.html. |