Archive · 21 Dec 2025
Super Flu Spreads Rapidly Across US
A new type of flu called 'super flu' is spreading quickly across the US.
This flu, called H3N2 subclade K, is different from what the flu shot was made to protect against.
Even though the vaccine might not be as effective, doctors say it still helps prevent serious illness.
People are also getting sick with norovirus, which causes stomach problems.
Schools are seeing many kids stay home because they are sick.
With lots of people traveling for the holidays, doctors are worried more people will get sick.
They advise staying home if you feel unwell, washing your hands often, and getting vaccinated to stay safe.
A new flu variant, H3N2 subclade K, is the dominant strain in the US, making up 89% of H3N2 cases since late September.
The current flu vaccine may not be as effective against this new variant, but it still helps prevent severe illness.
Flu cases have risen sharply, with 4.6 million cases, 49,000 hospitalizations, and 1,900 deaths reported so far this season.
Norovirus, known as the 'winter vomiting disease,' is also spreading widely, with a 69% increase in viral levels since October.
Holiday travel, with an estimated 122 million people traveling, could worsen the spread of these illnesses.
- Who
- Health officials, travelers, and vulnerable groups
- What
- A new flu variant (H3N2 subclade K) and norovirus are spreading rapidly
- When
- Ahead of the holiday travel rush, with flu activity rising sharply in mid-December
- Where
- Across the United States, particularly in the Northeast and Midwest
- Why
- The flu vaccine may not be as closely matched to the current dominant strain, and holiday travel increases the risk of spread
- Dominant Flu Variant
- H3N2 subclade K
- Flu Cases
- 4.6 million
- Hospitalizations
- 49,000
- Flu Deaths
- 1,900
- Norovirus Increase
- 69% since October
- Holiday Travelers
- 122 million