COVID could have pushed a number one seasonal flu pressure to extinction

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Enlarge / A bottle of influenza vaccine at a CVS pharmacy and MinuteClinic on September 10, 2021, in Miami.

The pandemic coronavirus’ debut wrought common havoc—not even seasonal flu viruses had been spared. Amid journey restrictions, quarantines, closures, bodily distancing, masking, enhanced hand washing, and disinfection, the 2020-2021 flu season was all however canceled. That meant not simply an unprecedented international lower within the variety of individuals sick with the flu but in addition a dramatic collapse within the genetic variety of circulating flu strains. Many subtypes of the virus all however vanished. However most notably, one complete lineage—one in every of solely 4 flu teams focused by seasonal influenza vaccines—went utterly darkish, seemingly extinct.

Researchers famous the absence final yr because the flu was nonetheless struggling to get better from its pandemic knockout. However now, the flu has come roaring again and threatens to trigger a very nasty season within the Northern Hemisphere. Nonetheless, the influenza B/Yamagata lineage stays lacking, in accordance with a research printed this week within the journal Eurosurveillance. It has not been definitively detected since April 2020. And the query of whether or not it is actually gone extinct lingers.

What B/Yamagata’s absence would possibly imply for future flu seasons and flu photographs additionally stays an open query. For a fast refresher: 4 principal varieties of seasonal flu have been circulating globally amongst people lately. Two are influenza kind A viruses: subtypes of H1N1 viruses and H3N2 viruses. The opposite two are influenza kind B viruses: offshoots of the Victoria and Yamagata lineages. (For a extra detailed clarification of influenza, try our explainer right here.) Present quadrivalent vaccines goal season-specific variations of every of those 4 varieties of flu viruses.

Having fewer flu viruses round means it could possibly be simpler to match future vaccines to circulating viruses, making seasonal photographs more practical. However, a shock re-emergence of B/Yamagata may turn out to be extra harmful as time passes and folks lose immunity. However, earlier than well being consultants can recreation out future influenza seasons, they’d prefer to know if B/Yamagata is really gone.

Vanished virus

In an article printed this week within the journal Eurosurveillance, researchers within the Netherlands sifted by way of the most recent international influenza surveillance information as much as August 31, 2022, searching for the lacking pressure. They word that GISAID, a world database of influenza virus genetic sequences that usually will get hundreds of flu sequences every year, has not acquired a single B/Yamagata sequence with specimen assortment information after March 2020.

The World Well being Group’s FluNet surveillance information has had a small variety of reviews of the lacking lineage—43 in 2021, largely from China, and eight sporadic circumstances from 4 international locations in 2022. For comparability, there have been greater than 51,000 detections of B/Yamagata in 2018.

The authors recommend the small variety of circumstances within the final two years could also be faulty detections. Relatively than circulating viruses, they might merely be detecting signatures of B/Yamagata from vaccines that carry live-attenuated influenza viruses. Or, they could possibly be genetic contamination from inactivated-virus vaccines. This is not only a hypothetical. The authors word that a variety of B/Yamagata detections within the US and Scotland had been discovered to be from live-attenuated influenza vaccines fairly than actual circumstances of circulating virus.

The researchers name for flu surveillance laboratories to extend efforts to detect any Yamagata circumstances to find out if it is actually gone or simply mendacity low. “From a laboratory perspective, we expect it could be advisable to extend the aptitude and capability to find out the lineage of all detected influenza B viruses world wide as that is vital to find out the absence of B/Yamagata lineage viruses,” they conclude. Additionally they suggest that the World Well being Group arrange standards to outline when the lineage could possibly be declared “extinct” and what the results of what that declaration may be.

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