Current Flu Alert (December 2025)
As of December 2025, the Centers for Disease Control and Prevention (CDC) indicates that seasonal influenza activity is increasing in most areas of the United States, and overall respiratory illness activity (including flu, COVID-19, and RSV) is high nationally.
Key updates for the current 2025-2026 season:
- A new H3N2 variant, known as subclade K, is driving the current activity and has been causing early and busy seasons in other parts of the world.
- The current flu vaccine offers protection against severe outcomes from the circulating strains, including subclade K, even if it is not a perfect match.
- CDC estimates that, as of early December 2025, there have been at least 1.1 million flu illnesses, 11,000 hospitalizations, and 450 deaths this season.
The CDC strongly recommends that everyone ages 6 months and older receive an annual flu vaccination. Antiviral drugs can be used to treat the flu, particularly for high-risk patients, and should be started as early as possible.
Earlier 2025 Alerts/Reports
Earlier in 2025, the CDC issued several notable communications:
- January 16, 2025 Alert: The CDC issued an advisory for clinical laboratories to accelerate the subtyping of influenza A positive specimens from hospitalized patients to quickly determine if they were a seasonal flu type or a novel virus, such as avian influenza A H5N1.
- H5 Bird Flu Cases: Throughout 2025, the CDC provided updates on human infections with avian influenza A(H5) viruses, primarily in individuals with exposure to infected dairy cattle or poultry. As of the latest reports, human-to-human transmission has not been identified in the U.S..
- 2024-2025 Season Summary: A September 2025 report summarized the prior season (2024-2025) as one of high severity, noting the highest cumulative hospitalization rate since the 2010-2011 season.
- 2025-2026 Season Outlook: An August 2025 outlook projected the 2025-2026 season would likely be of moderate severity but noted that the occurrence of back-to-back high-severity seasons was possible.
For the most up-to-date information, the public and healthcare professionals can monitor the CDC’s official “What’s New | Influenza (Flu)” page and the “Weekly US Influenza Surveillance Report” on the CDC website.
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