(New York Times) – Here’s what to know about the dominant version of the virus that’s circulating now.

The flu constantly morphs and mutates. Often, it surprises researchers a little.

This year, the virus is surprising them a lot.

They are bracing for a brutal season, driven by a new and alarming variant that is expected to circulate widely.

The main version of flu spreading in the United States right now is H3N2 subclade K. H3N2 is a common strain, but the specific type of it circulating now — subclade K — is what’s new. The variant has several mutations that differentiate it from previous versions, making it a “cousin of what we’ve always had,” said Dr. Scott Roberts, an assistant professor of infectious diseases at the Yale School of Medicine. (Read More)