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.