Genotype A3 #influenza #H5N1 isolated from fur #seals shows high virulence in #mammals, but not #airborne transmission
Abstract The global spread of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b viruses has recently extended to include diverse mammalian species , raising new concerns about pandemic risk . In 2023, this clade was first detected in Russian marine mammals during a mass mortality event among northern fur seals in the Far East . Genetic analyses revealed the causative viruses to belong to genotype A3 of European origin , which is known to have circulated in wild birds across the Far East since 2022. Notably, these isolates harbor the mammalian-adaptive substitutions PB2-K482R and NP-N319K—mutations previously linked to enhanced virulence in non-H5 avian influenza viruses , but whose impact on A(H5N1) clade 2.3.4.4b viruses remained to be characterized. The heightened virulence of A3 genotype viruses is confirmed by data obtained via a mouse model . However, despite these adaptive changes, ferret transmission models showed no evidence of airborne transmission of the fur seal...