Jan. 5, 2026, 1:32 p.m. ET
- A new flu variant is causing a surge in cases, with 32 states reporting “high” or “very high” activity levels.
- The Indiana Department of Health has reported Indiana to be at a “very high” level.
- The most common strain is a mutation of influenza A(H3N2), which may be better at evading existing immunity.
- Health officials recommend the flu vaccine for everyone 6 months and older to prevent serious illness.
A new flu variant has been sweeping across the nation, with millions of reported cases and the number of hospitalizations has doubled in a surge doctors say may not end for weeks.
Flu activity is at “high” or “very high” levels in 32 states and jurisdictions, according to a Dec. 30 Centers for Disease Control and Prevention report. According to the Indiana Department of Health, Indiana is one of the states at a “very high” level.
Hospitalizations nearly doubled in just one week, climbing to 19,053 from 9,944 the week before, based on CDC data. About 3,100 deaths have been reported nationwide. Additionally, the count of pediatric deaths has increased to five, up from two the week before. According to data from the Indiana Department of Health, there have been 17 deaths in our state this flu season.
Influenza A(H3N2) viruses are the most frequently reported flu viruses this season. Here’s what Hoosiers need to know.
Indiana Department of Health’s influenza-like illness dashboard
The Indiana Department of Health has its own dashboard for tracking influenza-like illnesses that is updated weekly on Mondays.
An influenza-like illness (ILI) is defined as an illness that has symptoms of a fever of 100 degrees or more and a sore throat and/or cough.
At the time of publication, the Indiana Department of Health has ranked the state at an ILI Activity Code of “Very High.”
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What is the new flu strain? Does vaccine work against it?
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 2025-26 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.
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
Katie Wiseman is a trending news reporter for IndyStar and Midwest Connect. Contact her at klwiseman@gannett.com. Follow her on Bluesky @katiewiseman
