The emergence of the pandemic coronavirus has wreaked havoc around the world. Even seasonal influenza viruses were no exception. Amid travel restrictions, quarantines, lockdowns, physical distancing, masking, increased hand washing and sanitizing, the 2020-2021 flu season has all but been canceled. Not only has it declined globally to an unprecedented level, but it also means that the genetic diversity of circulating influenza strains has collapsed dramatically. Many subtypes of the virus have nearly disappeared. But most notably, one entire lineage, one of the four influenza groups targeted by seasonal flu vaccines, completely faded and appeared to be extinct.
researcher pointed out last year’s absence The flu was still struggling to recover from the knockout of the pandemic. is. A study published this week in the journal EurosurveillanceSince April 2020, it has not been definitively confirmed. The question remains as to whether they are truly extinct.
An open question also remains about how the absence of B/Yamagata will affect future influenza seasons and influenza vaccination. A quick refresher: Four main types of seasonal flu have circulated around the world in recent years. Two are influenza A viruses, subtypes of the H1N1 virus and his H3N2 virus. The other two are influenza B viruses, branches of the Victoria and Yamagata lineages. (Read more about influenza here.) here is our explainer.) Current quadrivalent vaccines target season-specific versions of each of these four influenza viruses.
Fewer influenza viruses means that future vaccines will be easier to adapt to circulating viruses, making seasonal vaccinations potentially more effective. Meanwhile, B/Yamagata’s sudden reappearance could become more dangerous as time goes on and people lose immunity. , wants to know if B/Yamagata is really gone.
In an article published this week in the journal Eurosurveillance, Dutch researchers sifted through the latest global influenza surveillance data through August 31, 2022, looking for missing strains. They noted that GISAID, a global database of influenza virus gene sequences that typically retrieves thousands of influenza sequences each year, has not received a single B/Chevron sequence containing sampling data since March 2020. doing.
There were few reports of missing strains in the World Health Organization’s FluNet surveillance data. In 2021, 43 cases were reported, mainly from China, and in 2022, he reported eight sporadic cases from four countries. For comparison, B/Yamagata has over 51,000 detections of him. 2018.
The authors suggest that a small number of cases over the past two years may be false positives. It is possible that he is simply detecting B/Yamagata’s signature from a vaccine that carries a live, attenuated influenza virus rather than circulating the virus. Alternatively, genetic contamination from inactivated virus vaccines is possible. This is no mere hypothesis. The authors note the high number of detections of B/Yamagata. in the United States and Scotland turned out not to be an actual case of circulating virus, but from a live attenuated influenza vaccine.
The researchers are calling on the Flu Surveillance Institute to step up its investigation efforts to determine if the number of infected people in Yamagata Prefecture has really disappeared or if they are just lying around. “From a laboratory perspective, we believe it is prudent to increase our ability and ability to determine the lineage of all influenza B viruses detected worldwide. ,” they conclude. They also suggest that the World Health Organization set criteria to define when a breed can be declared “extinct” and what the consequences of that declaration will be.