A New, More Severe Flu Variant Is Spreading in the U.S.: What Families Need to Know

As the 2025–2026 flu season begins, health experts are closely watching a new, more severe flu variant spreading across the U.S. Known as subclade K of the H3N2 strain, this mutation may spread more easily and lead to more intense illness. For families—especially those with young children, older adults, or chronic health conditions—understanding the risks, symptoms, and prevention steps is key to staying safe this season.