At a Glance
- Flu cases surge across the U.S. due to new subclade K variant.
- CDC estimates 7.5 million illnesses, 81,000 hospitalizations, 3,100 deaths so far this season.
- Only 42% of adults and children have received a flu vaccine this year.
- Why it matters: With a highly contagious variant and low vaccination rates, many Americans face higher risk of severe illness.
Flu cases are rising rapidly across the country as a new subclade K variant spreads, raising concerns about a potentially severe season.
New Variant Drives Surge
Subclade K, a mutated H3N2 strain, first sparked outbreaks in the UK, Japan and Canada and is now dominating U.S. flu activity. The CDC reports high or very high illness levels in more than half the states. Its contagiousness could lead to a severe season.
- 7.5 million illnesses
- 81,000 hospitalizations
- 3,100 deaths
Impact on States
New York recorded 71,000 cases in the week ending Dec. 20, the highest since 2004. Other states also report high levels.
| State | Cases (Dec. 20) |
|---|---|
| New York | 71,000 |
| Other | High |
Vaccination and Protection
Despite not being a perfect match, the current vaccine offers partial protection against subclade K and reduces hospitalization risk, according to a UK analysis. Only 42% of the U.S. population has been vaccinated. Health experts recommend vaccination for everyone 6 months and older, especially high-risk groups such as:
- Adults ≥ 65 years
- Pregnant women
- Young children
- Individuals with chronic conditions (asthma, diabetes, heart disease, weakened immune system)
Flu vaccines are formulated to protect against three influenza strains. The vaccine remains a good match against H1N1 and Type B strains that may circulate this year. Flu shots are available for all ages, and the nasal spray FluMist is approved for ages 2-49; some people may vaccinate themselves at home for the first time this year.
Key Takeaways
- Flu cases surge with new subclade K variant.
- Vaccination coverage remains low at 42%.
- The current vaccine still offers partial protection and reduces hospitalizations.

The flu season is underway, and timely vaccination and early treatment remain the best defenses against this rapidly spreading variant.

