Flu cases are rising in 46 states. Check maps and see how to stay safe

This story was updated to add new information.

A new flu variant is sweeping across the United States, causing millions of reported cases and doubling the number of hospitalizations in a surge doctors say the peak is weeks away.

Flu activity is at "high" or "very high" levels in 46 states and jurisdictions, according to the Centers for Disease Control and Prevention's report. Since the flu season began in October, at least 11 million people have contracted the illness.

Hospitalizations nearly doubled in just one week, climbing to 34,641 from 20,064 the week before, based on CDC data. About 5,000 deaths have been reported. Two pediatric flu-related deaths were recorded for the week ending December 27, bringing the total for the 2025–2026 season to nine.

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Influenza A(H3N2) viruses are the most frequently reported flu viruses this season.

States reporting very high or high cases of influenza

What is the new flu strain?

Subclade K (previously called A(H3N2) virus subclade J.2.4.1) is a mutation of influenza A H3N2. Influenza A is typically the virus associated with the term "flu" and has evolved into many different strains over time.

Each year, the seasonal flu shot is formulated to target the most commonly circulating strains. One of those, H3N2, has been present for decades, according to the CDC and the Gavi Vaccine Alliance, but its most recent mutation is different enough that the vaccine made to target H3N2 for the 2025-2026 season is not as effective against it.

Because it's structurally different, subclade K may also be better at dodging immune systems that have already built up protections against more familiar strains. This year's vaccine isn't useless against subclade K, however.

Preliminary data has shown that the vaccine is still providing protection and that rates of hospitalization and serious illnesses are comparable to last year in Europe, according to the Pan American Health Organization and research published in the medical journal Eurosurveillance.

Know symptoms of the flu

Doctors and health professionals are recommending that everyone 6 months and older get vaccinated against influenza during the flu season because the symptoms overlap with COVID-19's. Your immune system may be weakened by one infection, leaving you more vulnerable to others.

The flu and COVID-19 have several symptoms in common. Here's how you can tell between the two viruses:

How to protect yourself from the flu

It's not too late to get a flu vaccination. The CDC, the World Health Organization and other leading medical institutions consider it the most effective way to prevent serious illness from the flu. Everyone 6 months and older is eligible for the flu vaccine unless they have a specified medical condition, such as an allergy to its ingredients or a history of severe reaction to the shot.

Six habits for staying healthy this flu season

• Wash your hands frequently with soap and water. Scrub for 20 seconds to remove germs.
• Get the flu vaccine; it's not too late.
• Cover your mouth and nose with a tissue, not your hands, when sneezing or coughing.
• If you feel symptoms developing, don't go to work or school. This will prevent spreading the illness to others.
• Avoid touching your eyes, nose and mouth. If you touch something that's contaminated with germs, it can easily spread disease.
• Clean and disinfect your home frequently, especially surfaces that are touched often, such as doorknobs and countertops.

CONTRIBUTING Mike Snider, Mary Walrath-Holdridge

SOURCE USA TODAY Network reporting and research; Centers for Disease Control and Prevention