Will it Be Another Bad Flu Season?

Flu activity in the U.S. remains relatively low for now, but experts say it’s rising in many regions, and early signs suggest this season could turn out to be a rough one.

The uptick in flu cases we’re seeing right now is not unusual, says Andy Pekosz, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health. They typically start climbing around the Thanksgiving holiday before peaking in the winter and subsiding in the spring.

However, infectious disease and public health experts are monitoring the type of flu virus that’s spreading and how that might affect this year’s wave of illness.

“We always look at other countries in the Northern Hemisphere to see how their flu seasons are going,” Pekosz says. “And interestingly, in several countries, in particular Japan and England and even Canada, it looked like there was an earlier start to the flu season. And it was dominated by the H3N2 influenza virus,” in particular, a variant of the H3N2 virus, called subclade K, that may be able to evade some of the protections offered by the flu vaccine.

According to the University of Minnesota’s Center for Infectious Disease Research and Policy, this variant emerged at the end of the Southern Hemisphere’s flu season, which runs opposite to ours.

“What will be really important to see in the next couple of weeks is how quickly case numbers increase,” Pekosz says. “We like to see a gradual increase between Thanksgiving and Christmas, but if cases really start to spike up, then we might be in a situation where this [flu variant] is infecting more people because it’s evading that vaccine-induced immunity.”

The flu vaccine still protects 

That does not mean the flu vaccine is useless, doctors and public health experts stress.

The influenza vaccine provides protection for three flu viruses: an A(H1N1) virus, an A(H3N2) virus and a B/Victoria lineage virus. So even if this year’s vaccine doesn’t end up being a perfect match for one of the strains — and experts say it’s too early to tell if that’s the case — it can still provide protection from the others circulating.

“It’s also true that even when we say there’s a mismatch, the vaccine oftentimes continues to protect against severe disease better than it protects against infection,” Pekosz says. This is especially important for older adults, who are at higher risk of getting seriously sick from a flu infection.