This year�s flu season is shaping up to be one of the most punishing in recent memory, with hospitalizations climbing sharply and the CDC estimating 4.6 million flu cases nationwide so far�even as peak season is still weeks away.
Health officials say the surge is being driven by an unusually aggressive strain of influenza A, known as H3N2 subclade K, a variant that has quickly become dominant and is leaving doctors alarmed by both the speed and severity of illness. As of mid-November, the strain accounted for more than half of all flu cases in the United States, and there is little indication it is slowing down.
