Diversity in flu virus strains and lineages has declined during the COVID-19 pandemic, with some experts speculating the potential extinction of certain virulent strains, news reports revealed.
Over the years, flu continuously evolves to weaken and evade immune defenses developed by humans to fend them off and in the years leading up to the pandemic, one of the Influenza A subtypes began to evolve in a strange way, according to health news media STAT.
COVID-19 precautions have forced people to adhere to social distancing and mask-wearing, with a direct result being flu infections dropping to historic lows.
Flu viruses consist of different strains, with new ones born continually. Several are difficult to treat and keeping pace with medicines that kill them is a continuous process.
As these strains mutate and distance from each other genetically, pharmaceutical companies are occasionally blind-sided in a treatment’s efficacy. One incident was seen over the winter period at the end of 2017 moving into 2018 when the particular flu jab developed to tackle the H3N2 strain failed to protect three-quarters of the people who took it in the US.
There has been recent speculation about how the H3N2 and B/Yamagata clades could be extinct due to the COVID-19 pandemic. STAT reported that no cases were recorded of either of these two virus strains throughout the pandemic. Experts do not yet know whether the strains are extinct or not but have said that if they were, it would make the process of creating the flu shot a lot easier.
“I think it has a decent chance that it’s gone. But the world’s a big place,” Seattle-based computational biologist at the Fred Hutchinson Cancer Research Center Trevor Bedford said, in reference to the H3N2 clade, according to STAT. He added that the last time any cases of the two strains were uploaded into international databases was back in March 2020.
The two key families of viruses that cause disease in humans are influenza A and influenza B. Flu A viruses are often transmitted in two subtypes: H1N1 and H3N2. The difference is that H3N2 viruses are more diverse than H1N1.
Whereas Flu B does not have subtypes it is divided into two lineages: B/Victoria and B/Yamagata. In recent years, the flub jab was adapted to include one version of each of the H1N1 and H3N2 viruses as well as the two flu B lineages.
Each year before flu season, scientists create a flu vaccine based on which strains are the most prevalent across the world and they then make informed predictions about which ones are most likely to become more common during the upcoming season.
If there really is less diversity among flu viruses, it would make the pool of circulating viruses a lot smaller for experts to choose from and hence easier to develop the shot.
Before the pandemic, the H3N2 clade was becoming more genetically diverse and complex with each passing year, STAT reported, adding that a drop in the strain’s diversity would be advantageous.
“There had been maybe five-ish, six-ish [H3N2] clades circulating and now there’s two or three that made it through that bottleneck,” said Bedford.
Director of the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, based at St. Jude Children’s Hospital in Memphis, Richard Webby told STAT: “Currently when we sit down to make recommendations for vaccine strains, it’s always the headache virus.”
“Without a doubt, this is definitely going to change something in terms of the diversity of flu viruses out there. The extent to which it changes and how long it stays changed are the big question marks. But we have never seen this before,” added Webby.
He predicted that the H3N2 strain will lose “a little bit” of diversity but cautioned that the flu virus B lineages could go quiet for a while and reappear again later.