Two Flu Varieties Seem to Have Disappeared During Lockdown


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  • Two varieties of flu have not been spotted for over a year, STAT reported.
  • Public-health measures to control the coronavirus pandemic may have led these strains to disappear.
  • It’s still possible, however, that they are circulating undetected.
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It’s been a lonely year to be an influenza virus.

Infectious-disease protections put in place during the coronavirus pandemic to protect people from COVID-19, such as mask requirements, school closings, and travel restrictions, made it nearly impossible for flu viruses to travel as well as they normally do.

The US, for instance, saw a 98% decrease in hospitalizations for flu in the 2020-2021 season. Rates in the UK dropped by 95%.

This was not just a result of sick people staying out of the clinic during the pandemic.

“There was a lot of flu testing happening — there was just not a lot of flu virus,” Alicia Budd, a Centers for Disease Control and Prevention epidemiologist, told Insider during a recent Association of Health Care Journalists fellowship. “The peak — if you can call it that — was 0.4% of the specimens tested for flu were positive.”

Normally during the height of flu season in the US, the share of positive tests ranges from 24% to 30%.

In fact, it’s possible that the sharp drop in flu cases has been so dramatic this year that it killed off some versions of the flu. Two varieties haven’t been seen for over a year, STAT reported. That could make it easier for vaccine makers to build a better flu vaccine — one targeted at a dwindling number of threats.

But experts caution it is still too early to draw any conclusions, in part because there were so few positive flu tests recorded last season.

“The actual number of specimens this year compared to previous seasons is extremely low,” Budd said.

“It’s obviously still important to know what viruses are out there,” she continued, adding: “That helps us understand a little what we might be on the lookout for this coming season and if there are updates that are needed to the vaccine.”

2 flu viruses have been missing from databases for over a year

coronavirus flu shot

An ad offering free flu shots in New York City on August 21.

John Nacion/SOPA Images/LightRocket/Getty Images

The flu-virus family is split into two types: A and B. Type A is made up of subtypes, two of which account for most type A flu viruses in people: H1N1 and H3N2. Those are further broken down into clades. Type B influenza, meanwhile, is split into two lineages, B/Victoria and B/Yamagata, which are also subdivided into clades.

Since March 2020, there have been no reports of one particular clade of H3N2 (called 3c3.A), according to GISAID, a global database in which researchers register and track which flu viruses are circulating.

“I do think we’re likely to lose a little bit of the H3N2 diversity,” Richard Webby, a flu expert at St. Jude Children’s Research Hospital, told STAT.

He said that’d be a “great thing” for the annual decision-making about which strains to target with vaccines — a process Webby takes part in each year.

“Currently when we sit down to make recommendations for vaccine strains, it’s always the headache virus,” he said of H3N2.

flu vaccine strains lab testing

Medical technicians at the Research Institute for Tropical Medicine virology lab performing tests for viruses including dengue fever, H1N1 influenza, and HIV/AIDS, in Manila in 2009.

Jay Directo/AFP via Getty Images

Read More:Two Flu Varieties Seem to Have Disappeared During Lockdown

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