A Second Wave of Flu May Be On the Way, CDC Warns

Flu season may have peaked in February, but we’re not out of the woods yet.

The bulk of this year’s deadly flu season was dominated by the H3N2 virus, an influenza A strain that is more severe and less receptive to vaccines than other types of the disease. As the season winds down, however, influenza B has overtaken influenza A, setting the scene for a possible second wave of flu, according to Centers for Disease Control and Prevention (CDC) data.

While flu activity nationwide has dropped to just above non-flu-season levels, influenza B viruses were reported more frequently than influenza A viruses during the week ending March 17, according to the CDC. Influenza B infections, which commonly strike later in the season, may be especially severe for young children, a CDC spokesperson told CNN.

Even those who already got the flu this year may not be safe, since it’s possible to get sick with both influenza A and influenza B in a single season.

The good news, however, is that influenza B viruses traditionally respond better to vaccines than influenza A viruses. By CDC estimates, this year’s flu shot was 42% effective against influenza B, versus 25% effective against H3N2.

And believe it or not, it’s still not too late to get a shot if you haven’t. The CDC recommends vaccination “as long as flu viruses are circulating” — and with 17 states still reporting widespread flu activity, that puts us squarely within that window.