INDIANA — A potent and highly contagious “super flu” strain is rapidly spreading across the United States, and health experts are warning that this year’s standard flu vaccine may offer little protection against it.
The strain, known as subclade K (a variant of Influenza A/H3N2), has become the dominant force in the 2025-2026 flu season. According to recent data from the Centers for Disease Control and Prevention (CDC), early sampling shows that roughly 89% to 90% of all Influenza A viruses tested were positive for this specific strain.
The impact of subclade K is already being felt in hospitals nationwide. As of Friday, the national hospitalization rate for flu-related illnesses jumped by 14.3%.
While the virus is spreading in every state, officials have identified “hot zones” where the spread is particularly aggressive:
- Rapid Spread: New York, Louisiana, and Colorado.
- High Rates: New Jersey and Rhode Island.
- Elevated Hospital Visits: Georgia, New Mexico, Idaho, Michigan, North Carolina, South Carolina, Massachusetts, Connecticut, Maryland, and Washington, D.C.
The Situation in Indiana
Indiana is not immune to the surge. As the virus moves through the Midwest, local data reflects a growing concern for Hoosiers:
| Metric | Indiana Status (Current Week) |
| Activity Level | Moderate to Increasing |
| Dominant Strain | Influenza A (H3N2) Subclade K |
| Regional Positivity | 8.1% – 14.8% (HHS Region 5) |
Public health laboratories in the region report that Influenza A accounts for over 94% of positive specimens, with the majority falling under the “drifted” subclade K that evades the current vaccine’s primary targets.
The “super flu” is difficult to manage because subclade K was not included in the original formulation of this year’s flu shot. Experts at The Hill report that the vaccine does not adequately cover this specific Influenza A strain—the version of the virus traditionally responsible for the highest number of deaths among the elderly.
“Even though the match isn’t perfect, it is still worthwhile to get the shot,” health officials noted. “Vaccination can still lessen the severity of symptoms and prevent the most deadly complications.”
CDC officials urge the public to watch for the following symptoms:
- High fever and chills
- Persistent cough and sore throat
- Muscle aches and severe fatigue
- Headaches and runny nose
- Occasionally, vomiting or diarrhea (more common in children)
While most healthy individuals recover within two weeks, complications like pneumonia remain a deadly threat, particularly for those with underlying conditions. With the season expected to peak in February, experts warn that the virus will likely reach every corner of the country before the winter is over.
