Last fall’s predicted surge of influenza cases, driven by the new “subclade K” mutation, is hitting U.S. emergency rooms as holiday get-togethers put people in close spaces where the flu virus can ...

A flu variant called subclade K emerged too late to be fully covered by this year's vaccine. But the flu shot can still help protect you.

California could see an early start to the annual flu season, as a combination of low vaccination rates and late mutations to the virus may leave the state particularly exposed to transmission, health ...

California public health officials cautioned more children are testing positive for the flu this season. Here are flu ...

As the COVID-19 pandemic progresses, researchers say it is important to track how the coronavirus mutates because it could affect the efficacy of a vaccine. Like all living cells, viruses evolve their ...