Highly Pathogenic Avian Influenza A(H5N1) Viruses from Multispecies Outbreak, Argentina, August 2023

Abstract

We report full-genome characterization of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus from an outbreak among sea lions (August 2023) in Argentina and possible spillover to fur seals and terns. Mammalian adaptation mutations in virus isolated from marine mammals and a human in Chile were detected in mammalian and avian hosts.

Keywords: Argentina; HPAI H5N1; South America; highly pathogenic avian influenza virus H5N1; influenza; mammalian adaptation; mammals; pinnipeds; seabirds; transmission; viruses.

Figure

Maximum-likelihood trees for hemagglutinin (A) and polymerase basic 2 (B) gene segments evaluated in study of highly pathogenic avian influenza A(H5N1) in Argentina compared with reference strains from other countries in South America. Tree areas have been enlarged at right to show detail. Red arrows indicate virus from marine mammals in Argentina; red asterisk indicates virus from a tern in Argentina. Black arrowhead along full tree in panel A indicates the hemagglutinin sequence from the first detection of HPAI H5N1 in a wild goose in Argentina. Node shape represents host group, and node color (and bars adjacent to trees) represents the region/country. Branch lengths are drawn proportionally to the extent of changes. Values adjacent to nodes represent bootstrap support >40. Scale bars indicate nucleotide substitutions per site.