The 2019-2020 flu season is up and running—and so far, it’s off to a weird start.
Flu activity has been elevated since the start of November and is only expected to continue climbing, the Centers for Disease Control and Prevention reports in its latest flu update. That’s a few weeks earlier than in past years.
Flu season in the United States can ramp up in the fall and peak anywhere between December and March, then drag itself out as late as May. In the last 36 years, flu most often ramped up in December and January and peaked in February. But for this winter, the CDC says there’s a 40 percent chance the flu will peak in December based on activity so far.While this season may peak on the early side, the most unusual aspect is that it’s being driven by an influenza B strain. This isn’t necessarily good or bad, just unusual.
Type B is one of three types of influenza viruses that infect humans—A, B, and the very mild C. (There’s a fourth type, D, but so far it mainly seems to infect cattle.) Most flu seasons are driven by type A viruses, the kind you’ve probably heard about the most. Type A viruses are identified by numbered Hs and Ns, like H1N1 and H3N2.