Flu season could be nasty this winter

"The U.S. may be entering another rough winter for flu, according to early data. "The signs are, it could be a big season," says Richard Webby, who studies the flu at the St. Jude Children's Research Hospital in Memphis. "The flu season might have a little bit of a punch to it this year." The first clue to what may be in store is what influenza did during the southern hemisphere's winter."

""They had some pretty decent flu activity in many parts of the southern hemisphere," Webby says. "It actually lasted for a longer period of time the tail of the season went on for longer than typical." And now parts of the northern hemisphere, such as the U.K., are getting hit hard. That often foreshadows what's in store for the U.S."

""There is basically a new variant of influenza circulating that has mutated a little bit," says Caitlin Rivers, an epidemiologist at Johns Hopkins. "And that means that it's just different enough from what your body or the vaccine may recognize that it can kind of get around those protections." And she says the flu shot this year, "may not be as good a match as if we hadn't seen this new variant.""

Early surveillance shows increased influenza activity in the southern hemisphere and emerging surges in parts of the northern hemisphere, signaling potential for a larger U.S. season. The dominant strain so far in the northern hemisphere is H3N2, which tends to produce more severe disease and higher activity. A recently evolved H3N2 variant has become dominant in the U.S. and carries mutations that reduce recognition by prior immunity and may lessen vaccine match. U.K. data indicate vaccines still reduce severe outcomes, with about 70–75% protection against pediatric hospitalization. Vaccination and monitoring remain important despite potential reduced effectiveness.

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