Summary
A new mutation of the flu virus has caused a sharp increase in flu cases in the U.S., with hospitalizations reaching over 33,000 by the end of 2025. This year's flu vaccine does not fully match the dominant strain but still offers protection against severe illness and death, according to doctors.
Key Facts
- U.S. flu cases have risen dramatically, with over 11 million people affected and more than 5,000 deaths reported this flu season.
- Hospitalizations increased from under 7,000 in early December to over 33,000 by the end of 2025.
- The surge is connected to a new mutation of the influenza A virus called "subclade K," which the current vaccine does not cover well.
- Each year, scientists predict which virus strains to include in the flu vaccine months in advance.
- The current vaccine covers three strains: two strains of influenza A (H1N1 and H3N2) and one strain of influenza B (Victoria lineage).
- Despite the mismatch with the new strain, doctors recommend getting vaccinated, as it reduces the risk of severe illness and death.
- The flu vaccine provides protection against other circulating flu strains, not just the new, mutated one.
