U.S. CDC classifies 2025–26 flu season as ‘moderately severe’ as infections and hospitalizations climb

CDC warning as flu activity rises

U.S. seasonal influenza activity remained elevated heading into 2026, and the Centers for Disease Control and Prevention has classified the 2025–26 flu season as “moderately severe.” A Reuters report published January 5, 2026, cited CDC data showing activity rose in the final week of December, with the agency estimating at least 11 million illnesses, 120,000 hospitalizations and 5,000 deaths so far this season at the time of the report.

Public health experts speaking to Reuters pointed to several drivers behind the surge, including increased holiday travel, low vaccination rates in some communities, and the spread of misinformation about vaccines and illness prevention. The CDC also warned that flu activity was likely to remain elevated for several more weeks.

What’s circulating

Reuters reported that influenza A(H3N2) was the dominant strain, accounting for more than 91% of subtyped influenza A cases in CDC data at that time. The report also noted that genetic characterization of collected viruses showed a large share belonging to a specific subclade, reflecting how seasonal strains can shift during a single winter.

What people can do now

• Vaccination: even with imperfect strain matching, shots can reduce the risk of severe disease for many people.
• Early treatment: high-risk individuals should seek medical advice quickly if flu symptoms develop.
• Prevention basics: masking in crowded indoor spaces, hand hygiene, and staying home when ill can reduce spread.

As the season continues into late January and beyond, local conditions can vary substantially. Health departments typically advise checking regional flu activity levels and hospital capacity updates, especially for families with infants, older adults, or immunocompromised household members.