Many subtypes of the [influenza] virus all but vanished. But most notably, one entire lineage—one of only four flu groups targeted by seasonal influenza vaccines—went completely dark, seemingly extinct.
Researchers noted the absence last year as the flu was still struggling to recover from its pandemic knockout. But now, the flu has come roaring back and threatens to cause a particularly nasty season in the Northern Hemisphere. Still, the influenza B/Yamagata lineage remains missing.
Having fewer flu viruses around means it could be easier to match future vaccines to circulating viruses, making seasonal shots more effective. On the other hand, a surprise re-emergence of B/Yamagata could become more dangerous as time passes and people lose immunity. But, before health experts can game out future influenza seasons, they’d like to know if B/Yamagata is truly gone.
In an article published [recently] in the journal Eurosurveillance, researchers in the Netherlands sifted through the latest global influenza surveillance data up to August 31, 2022, looking for the missing strain. They note that GISAID, a global database of influenza virus genetic sequences that typically gets thousands of flu sequences each year, has not received a single B/Yamagata sequence with specimen collection data after March 2020.
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The researchers call for flu surveillance laboratories to increase efforts to detect any Yamagata cases to determine if it’s truly gone or just lying low.
