Emergence and spread of NA-I223V and NA-S247N double-mutant #H1N1pdm09 #influenza viruses with reduced #oseltamivir susceptibility in the #Netherlands and beyond, 2023 to 2026

 

Abstract

In 2023/24, A(H1N1)pdm09 influenza viruses with neuraminidase (NA)-S247N emerged in NA-clade C.5.3.3 carrying NA-I223V, spread internationally, then faded. Such double mutants reappeared sporadically in 2024/25. They expanded again in 2025/26 in NA-clade D.3 viruses carrying NA-S247N after acquiring NA-I223V in Europe – notably Spain, the Netherlands, Finland and France, and beyond. Dutch double mutants from both seasons showed median 12- and 13-fold reduced inhibition by oseltamivir. These findings underscore the need for ongoing genomic and phenotypic monitoring of antiviral susceptibility.

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Source: 

Link: https://doi.org/10.2807/1560-7917.ES.2026.31.36.2600733

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