Why We’re Seeing a Deadlier Flu Season Than We’ve Seen in Years

It's all about those strains.


The 2017-2018 flu season is shaping up to be more nasty than recent years. According to the U.S. Centers for Disease Control and Prevention, 13 children have already died from the flu this season. USA Today reports that some states are reporting much higher rates of flu-related hospitalizations than at this point one year ago.

What makes this season more threatening than others? Well, there’s a very specific reason, and it has to do with which particular type of flu strain is dominant this year. You see, the sickness you get from the flu is actually caused by a bunch of different strains of the influenza virus. This flu season, influenza A(H3N2) is the dominant strain, and it’s a biological bully.

Influenza A(H3N2) is the dominant flu strain this flu season, and it's exceptionally yucky.National Institutes of Health

Historically, flu seasons where influenza A(H3N2) was the dominant strain saw more young people and people 65 years or older being hospitalized or dying when compared to people in the middle of that age range. But it’s not just that A(H3N2) is a stronger viral strain — it’s also harder to vaccinate against.

“[I]nfluenza vaccine effectiveness (VE) in general has been lower against A(H3N2) viruses than against influenza A(H1N1)pdm09 or influenza B viruses,” reads a CDC announcement from the end of December 2017. “Last season, VE against circulating influenza A(H3N2) viruses was estimated to be 32% in the U.S.”

That is not a great success rate for a vaccine, but it’s not necessarily because the vaccines are ineffective. That’s just how the flu vaccine works. The flu mutates so much from year to year that it’s really hard to effectively cover all our viral bases with a single vaccine. Usually, the flu vaccine you get at the doctor or drug store includes deactivated cells from two types of influenza A (H1N1 and H3N2) and influenza B. These cells, in combination with immune system irritating “adjuvants” help prep your immune system to fight off viral infection.

But unfortunately, these vaccines are just our best guess attempt at preempting the impact of flu in what has always been a perpetual viral arms race. For this reason, the CDC is recommending that all doctors who might be treating flu patients — which, to be clear, is all doctors who treat any patients — should also have antiviral medications on-hand.

And even though the success rate of the flu vaccine is relatively low, it’s still a good idea to get it. It will help protect you and your friends, family, and co-workers. It looks like this season, we need every weapon we can get.