More than a year after the Corona pandemic began, the coronavirus is still gripping the world. But scientists are already looking at the influenza virus with concern. They believe the next flu season could be particularly severe.
Is there a threat of a major influenza wave after the Corona pandemic?
The current flu season was almost entirely absent, thanks to Corona protections. In the U.S., there have been only 2,000 lab-confirmed cases of flu so far this season – there are usually already around 200,000 this time of year, according to editor Lauren Dunn on the NBC News portal. Worldwide, there are between nine and 45 million cases each flu season.
Thanks to protective measures against the coronavirus, the influenza virus had virtually no chance to spread this year. However, that hasn’t been all upside. According to Dr. Andy Pekosz, professor of microbiology at the Johns Hopkins Bloomberg School of Public Health, a low flu year is often followed by a particularly high flu year. There are several reasons for this.
Barely any immunity to current flu strains.
“We now have a period of more than a year in which a significant portion of the population has not contracted influenza and thus gained immunity,” Pekosz says. “This could mean that the population’s susceptibility to influenza will increase.”
If you catch the flu, you develop some immune protection against the virus. That’s why children are even more susceptible to catching influenza – their (partial) immunity has to build up. But with hardly anyone contracting influenza this year, the number of people without immune protection is particularly high.
More deaths from flu virus after Corona?
“Low immunity in the population may lead to more cases,” said Scott Hensley, a microbiologist at the Perelman School of Medicine at the University of Pennsylvania. “We might see more pediatric deaths and at the same time an increase in cases across the population. This is because overall population immunity is expected to be low.” With lower levels of immune protection, illness caused by the virus can be more severe.
Many influenza strains limit active ingredient of vaccines
“It’s interesting,” Hensley said. “Normally, there’s a lot of genetic diversity in these viruses.” That’s not the case this year, he said. It’s unclear whether there are actually fewer variants of the flu virus circulating, or whether fewer variants have been detected because of low infections.
“In general, we want less genetic diversity,” explains Sarah Cobey, an epidemiologist and evolutionary biologist at the University of Chicago. That’s because the lower the number of viral strains, the better the vaccine works. In recent years, the H3N2 flu strain had proved problematic because it had so many secondary strains, making it harder for the vaccine to protect against it. So far this year, only a few strains have been identified.
Extensive flu data important for vaccine development
At the same time, therein lies the problem, because the lack of data on flu virus strains could leave the next vaccine inadequate. “Because we had so few cases, we use a small number to make our selection,” Pekosz described. “There could be strains circulating with small numbers that could dominate. We usually worry about that every flu season, but usually we have a much larger data set to choose from.”
Flu viruses mutate faster than SARS coronaviruses
Although the influenza virus was first isolated more than 80 years ago, scientists say there is still much to learn. “What’s really challenging about influenza is that it evolves rapidly,” Cobey said, adding that influenza viruses seem to mutate faster than SARS-CoV-2. “Every year we see influenza viruses that have never been seen before on this planet.”
We can look forward to seeing if a major flu wave will hit us after the coronavirus pandemic. After all, we already have vaccines. Experts are advising people to be sure to get vaccinated against influenza for the next flu season.