Scientists have deemed the optimism about the "disappearance" of the flu strain to be excessive.

The fact that the B/Yamagata influenza virus strain is virtually nonexistent may be a consequence of anti-coronavirus measures, but it is possible that it will return at some point, virologists interviewed by RBC stated. They commented on the findings of American scientists who claimed that the strain disappeared following quarantines and mask mandates during the pandemic.

"To say unequivocally that reintroducing such quarantine measures will allow us to completely eliminate the influenza virus is, in my opinion, extremely optimistic. Therefore, we can attribute certain variability in the B-virus line to the covid-19 restrictions that were in place, but we definitely cannot predict that a repeat of such a global quarantine will help us cope with other influenza viruses. The only effective way to combat influenza today remains annual vaccination with updated vaccines," Sergei Voznesensky, associate professor of the Department of Infectious Diseases at RUDN University, told RBC.

Voznesensky noted that the influenza B virus itself is less contagious and does not cause epidemics, but rather spreads most often through localized outbreaks. It also doesn't cause as many fatalities, he explained.

Alexander Chepurnov, HEAD of the Laboratory of Particularly Dangerous Infections at the Federal Research Center for Fundamental and Translational Medicine (FRC FTM), also believes that there is no complete certainty that Yamagata has disappeared completely.

"It's possible that the virus has persisted somewhere in the human population, and then after some time it will re-emerge and return. For such a pathogen to disappear, it would be necessary for a sufficiently long period of time, a month for example, to be free of infection, so as to interrupt transmission. This is possible for pathogens that are strictly anthroponotic, associated only with humans, and lack the ability to parasitize other animals," Chepurnov noted. The virologist recalled that this was successfully achieved with the smallpox virus.

Earlier, scientists from the US National Center for Biotechnology Information (NCBI) concluded that self-isolation, wearing masks and other measures aimed at containing the spreadCOVID-19 led to the disappearance of the Yamagata B influenza virus strain. The study states that in recent decades, influenza epidemics were caused by four main strains, including Yamagata, but now scientists identify only three of them.

Experts now believe that a similar approach could be used to eradicate another, more common strain of influenza B, Victoria. However, this strain accounts for an average of 23% of annual flu cases worldwide, including 1.4 million hospitalizations.