What Is Influenza B? The Second Wave Of The Flu Is Here & This Is How To Prepare

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Hang tight, folks. It may technically be spring, but that doesn't mean the flu season is over. This year's superpowerful H3N2 strain saw the flu season in the U.S. peak with as many sick people as the 2009 outbreak of swine flu, Vox reported. But while we're over the peak, we're not out of the woods. And while we were all busy watching H3N2, another influenza strain snuck in and is now causing a "second wave" of the flu, according to The Cut.

The Centers for Disease Control's (CDC) weekly influenza report for the week ending Mar. 24 showed an overall decrease in cases of the flu around the U.S. Good news, but it comes with a catch: Though the number of folks with flu is decreasing in general, reports of influenza B viruses have overtaken reports of influenza A viruses. H3N2 is a strain of influenza A, so the influenza B strain showing up in patients across the country is a new beast altogether.

To break it down quickly, strains of influenza A include ones like swine flu, and H3N2. What makes them different from influenza B strains, according to WebMD, is that influenza A can hop between animals and humans, infecting us all. Influenza B strains, on the other hand, can only infect humans. Influenza B strains also do not cause pandemics, unlike influenza A, and are potentially less severe than A strains, but that's not a sure thing, WebMD reported.

“The dominant strains every year are one of the A strains. They create the big epidemics, Dr. William Schaffner, an infectious disease expert at Vanderbilt University, told Healthline. “Now, behind the scenes as it were there are influenza B strains that are circulating at the same time. They cause illness that is just as severe, but the B strains, for biological reasons that we don’t understand, don’t create big epidemics, but they smolder along.”

Stephen Ferrara, a flu expert and associate dean of clinical affairs at Columbia University School of Nursing, told The Cut that if a strain of influenza A is the dominant strain during a particular flu season, "a B strain usually isn't far behind." He said, "This is typical in a flu season. [Influenza] A strains drop and then we see a second wave of influenza B." Ferrara added that some folks hypothesize this happens because of temperature changes — e.g., when we start hitting springlike warmups, influenza B has a chance to rise up and tear us down just when we thought we were safe. But no one is entirely sure why B strains tend to be so opportunistic in the wake of A strains, he said.

While it doesn't seem like folks are expecting this second wave to match H3N2's virulence, you should still be vigilant, Ferrara told The Cut. "We don’t want to say, ‘Oh, it’s only influenza B, you don’t need to worry.' We don’t want to put out a false sense that it’s any less severe. Unfortunately, there will still be pediatric deaths this flu season, but there’s no need to panic. Influenza B tends to not be as contagious from person to person, so it’s slightly easier to prevent."

So, how do you prevent it? The same way you prevent all other flus: Wash your hands regularly, don't shy away from wiping down shared surfaces like break room lunch tables, and, of course, GET A FLU SHOT. If you already got one, there's a chance you're protected against the current strain of influenza B, but "there are all types of variables" that may mean you're not totally safe, Ferrara said, including the fact that "researchers haven’t yet definitively determined which strain of influenza B people in the 'second wave' are catching," The Cut reported. Additionally, if you already had the flu this season, that similarly doesn't mean you're immune, since the earlier flu was likely to be of the influenza A variety. If you do think you've caught the flu, you don't just have to ride it out at home; your doctor may be able to give you antiviral medication, which may shorten the duration and severity of the illness.

Having some protection is better than none, so, as always, a flu shot is a good idea. By nabbing yourself a flu shot and carrying on with other protective habits, you can minimize your chance of being caught up in the second wave.