Flu is rising rapidly across the U.S., driven by a new variant of the virus — and cases are expected to keep growing as holiday travel plays out. That variant, known as “subclade K,” led to early outbreaks in the United Kingdom, Japan and Canada. AdvertisementWhat is subclade K flu? The flu virus is a shape-shifter, constantly mutating, and it comes in multiple forms. But Hopkins’ Pekosz cautioned it will take time to tease apart whether this subclade K version simply spreads more easily or also is more dangerous.

Source: Los Angeles Times January 05, 2026 11:02 UTC