Significant December Spike in US Influenza Cases Following Severe 2024-2025 Season
The United States experienced a notable rise in influenza cases in December 2025, following the most severe flu season since 2018, according to data from the Centers for Disease Control and Prevention (CDC). By December 20, around 7.5 million flu cases and 81,000 hospitalizations were reported nationwide, representing a 25% increase in weekly hospitalizations. Thirty-two states recorded high or very high levels of illness during this period.
The 2024-2025 flu season was marked by a record-high 279 influenza-associated pediatric deaths. Overall, more than 3,100 influenza-related deaths occurred in the US in the year ending August 2025. A new influenza variant subclade K has also emerged, contributing to growing concerns about the virus's impact. Europe similarly encountered high to very high influenza activity in December.
Public health officials emphasized that it remains uncertain whether total flu cases will continue to rise this season or if the December surge was isolated. Vaccination is strongly recommended, particularly for children and older adults, to reduce illness severity and spread. However, fewer people may seek vaccination this season due to the CDC's cancellation of its flu vaccination campaign under Health Secretary Robert F. Kennedy Jr. Approximately 130 million flu vaccine doses had been distributed by early December, 13 million fewer than the previous year.
Antiviral treatments can be effective if administered promptly after symptom onset. Additionally, at-home influenza tests are now available at pharmacies to aid early detection and treatment.
