Flu Season Is Off to an Early (and Weird) Start

A person sick with a cold sitting on couch.
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Flu season is here, and it's off to a strange start.

The first unusual thing about this year's flu season is how early it arrived. There are now 12 U.S. states reporting high levels of flu activity (mostly in the South) and 15 states reporting moderate activity, according to data from the Centers for Disease Control and Prevention (CDC). For comparison, at this same time last year, just two states reported high levels of flu activity and three states reported moderate activity.

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What's more, most flu infections right now are being caused by a strain of the virus known as influenza B. That's pretty unusual — normally, flu season kicks off with influenza A strains (H1N1 and H3N2) predominating while influenza B shows up toward the end of flu season, in the spring.

Related: 6 Flu Vaccine Myths

"Generally, we see [influenza B] toward the tail end of the season," Dr. Bernhard Wiedermann, an infectious disease specialist at Children's National Hospital in Washington, D.C., told Healio, a news site for health care professionals. Indeed, a flu season that starts with influenza B has not been seen in the last 15 years that the CDC has been collecting this type of data, Healio reported.

"We haven't seen this predominance of influenza B in the 'modern' era when we have had ready access to rapid molecular testing," Wiedermann said. There could be another peak in flu activity with influenza A strains later in the season, he added.

The CDC estimates that there have been at least 1.7 million illnesses, 16,000 hospitalizations and 910 deaths from the flu so far this season.

But it's not too late to get a flu shot, the CDC said. Quadrivalent flu vaccines protect against two strains of influenza A virus and two strains of influenza B. Flu shots are recommended for everyone ages 6 months and older. 

Originally published on Live Science. 

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.