{Summary}
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Key Points
° Seasonal influenza activity remains low nationally, but multiple surveillance indicators have been increasing since late August/early September 2026.
° This early-season influenza activity is currently higher than typically observed at this time of year but an earlier increase in activity does not necessarily lead to a higher seasonal peak or greater overall severity.
° During Week 42 (the week ending October 24, 2026), of the 466 influenza viruses reported by public health laboratories, 456 were influenza A and 10 were influenza B. Of the 371 influenza A viruses subtyped during Week 42, 367 (98.9%) were influenza A(H1N1)pdm09 and 4 (1.1%) were A(H3N2).
° Since Week 21 (the week ending May 30, 2026), 82.7% of the influenza A viruses reported have been A(H1N1)pdm09 and among these, the majority have been D.3.1.1 HA subclade.
° The influenza A(H1N1) viruses detected this season are still A(H1N1)pdm09 viruses, which emerged in 2009 and have caused seasonal epidemics globally since then. Influenza viruses are constantly changing, often requiring updates to influenza vaccine viruses each season.
° Historically, influenza A(H1N1)pdm09 viruses have changed less often than A(H3N2) viruses. Recently circulating influenza A(H1N1)pdm09 viruses (which are in an HA subclade called "D.3.1.1") have divided into distinct groups with different genetic changes in their HA genes. We are seeing more genetic diversity among co-circulating A(H1N1)pdm09 viruses than we have before.
° It is too early to know what viruses may predominate or to say whether there might be implications on flu vaccine effectiveness this season.
° The first influenza-associated pediatric death occurring during the 2026-27 influenza season was reported to CDC this week.
° Because case investigation takes time, flu-associated deaths in children may be reported to CDC weeks after they occur; counts are preliminary and may increase. All reported cases meet the influenza-associated pediatric mortality case definition.
° CDC estimates in-season disease burden across all ages each week. CDC estimates that there have been at least 1,000,000 illnesses, 16,000 hospitalizations, and 900 deaths from flu so far this season.
° CDC's FluSight forecasts predict a likely increase nationally in both flu hospital admissions and the percentage of emergency department visits associated with flu for the week ending November 14, 2026. The number of new flu hospital admissions is forecast to range from 4,800 to 23,200 admissions, while the national percentage of emergency department visits due to flu is forecast to range from 1% to 4.4%.
° Annual seasonal influenza (flu) vaccination is recommended. Influenza vaccines are available for persons aged 6 months and older. People who are recommended for influenza vaccination but have not been vaccinated yet this season are encouraged to be vaccinated now.
° There are prescription flu antiviral drugs that can treat flu illness; those should be started as early as possible and are especially important for patients at higher risk for influenza complications.1
° Influenza viruses are among several viruses contributing to respiratory disease activity. CDC is providing updated, integrated information about COVID-19, flu, and respiratory syncytial virus (RSV) activity on a weekly basis.
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Source: US CDC, FluView, https://www.cdc.gov/fluview/surveillance/2026-week-42.html
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