CDC: U.S. Flu Season ‘Moderately Severe’ With 11M Illnesses

CDC classified the U.S. flu season ‘moderately severe’ after year-end data showed a sharp rise in infections and medical visits, signaling a difficult winter stretch ahead for hospitals and clinics nationwide.

What Happened

The Centers for Disease Control and Prevention said the share of outpatient visits for flu-like illness climbed to 8.2% in the week ending December 27, 2025—well above the national baseline of 3.1%. Flu activity is now elevated across most of the country, with dozens of jurisdictions reporting “very high” levels. The agency estimates at least 11 million illnesses, 120,000 hospitalizations, and at least 5,000 deaths so far this season, and expects elevated activity to persist for several weeks.

By The Numbers

Doctor visits for flu-like illness hit 8.2% during the final full week of December, according to CDC’s FluView. The agency also reported nine pediatric flu deaths to date this season. Laboratory data show influenza A(H3N2) is dominating circulation—more than 91% of subtyped A viruses—while genetic analysis indicates that about 90% of H3N2 samples characterized since late September belong to the K subclade. H3N2 subclade K is dominant, a factor public-health experts are watching as the season unfolds.

Vaccinations Lag Behind

CDC’s vaccination dashboard points to slower uptake compared with recent years. As of December 6, 2025, about 129.8 million flu vaccine doses had been distributed in the U.S. In retail pharmacies, roughly 31.0 million doses had been administered by November 29—about 2.1 million fewer than at the same point in the 2024–25 season. Physician offices had given about 16.7 million doses, roughly 873,000 fewer than a year earlier. Children’s coverage as of mid-December was about 42%, with adult coverage estimates in the low-to-mid 40% range—figures that leave substantial room for improvement.

Why It Matters

The combination of widespread transmission, an aging population, and lagging vaccination increases the risk of severe illness, particularly among older adults, very young children, and people with underlying conditions. While vaccines are not a perfect match every year, they continue to reduce the likelihood of serious outcomes. CDC also notes that prompt antiviral treatment can help high‑risk patients who become ill.

What’s Next

Health officials say the U.S. has not yet put the season behind it. With respiratory viruses typically peaking in January or February, the CDC continues to urge anyone 6 months and older who hasn’t received a flu shot to get one now, and to seek testing and care early if symptoms develop—especially those at higher risk of complications.

Sources

• US CDC says 2025–26 flu season ‘moderately severe’ as cases hit 11 million — Reuters (January 5, 2026)
• Weekly US Influenza Surveillance Report: Key Updates for Week 52, ending December 27, 2025 — CDC (December 27, 2025)
• Weekly Flu Vaccination Dashboard — CDC (December 23, 2025)