Archive · 31 Dec 2025
Flu Subclade K Rising Rapidly in US
There's a new type of flu called subclade K that's spreading quickly in the U.S. It's a version of the H3N2 flu virus, which can be pretty serious, especially for older adults.
The flu season is expected to get worse with holiday travel.
So far, there have been millions of illnesses, tens of thousands of hospitalizations, and thousands of deaths.
Only about 42% of people have gotten their flu shot this year.
The vaccine isn't a perfect match for subclade K, but it can still help prevent severe illness.
The CDC recommends that everyone 6 months and older get a flu vaccine, especially those who are at higher risk, like older adults, pregnant women, young children, and people with chronic health problems.
There are medicines to treat the flu, but they need to be taken soon after symptoms start.
A new flu variant, subclade K, is spreading rapidly across the U.S., with high or very high levels of illness in more than half the states.
The CDC reports at least 7.5 million illnesses, 81,000 hospitalizations, and 3,100 deaths from flu so far this season.
Subclade K is a mutated version of the H3N2 flu strain, which is known to be harsh, especially for older adults.
The current flu vaccine offers partial protection against subclade K and is recommended for everyone 6 months and older, particularly high-risk groups.
Prescription medicines are available for treating flu, but they need to be started within a day or two of symptoms beginning.
- Who
- General public, especially high-risk groups
- What
- Rising cases of flu subclade K variant
- When
- Current flu season, with data as of Dec. 20
- Where
- United States, with significant cases in New York
- Why
- Subclade K variant is spreading rapidly, and holiday travel is expected to increase cases
- Variant Name
- Subclade K
- Type of Flu
- H3N2
- Estimated Illnesses
- 7.5 million
- Estimated Hospitalizations
- 81,000
- Estimated Deaths
- 3,100
- Vaccination Rate
- 42%
- High-Risk Groups
- Older adults, pregnant women, young children, people with chronic health problems
- Treatment
- Prescription medicines for high-risk individuals