Cross-species and mammal-to-mammal transmission of clade 2.3.4.4b highly pathogenic avian influenza A/H5N1 with PB2 adaptations

Highly pathogenic H5N1 avian influenza viruses (HPAIV) belonging to lineage 2.3.4.4b emerged in Chile in December 2022, leading to mass mortality events in wild birds, poultry, and marine mammals and one human case. We detected HPAIV in 7,33% (714/9745) of cases between December 2022–April 2023 and sequenced 177 H5N1 virus genomes from poultry, marine mammals, a human, and wild birds spanning >3800 km of Chilean coastline. Chilean viruses were closely related to Peru’s H5N1 outbreak, consistent with north-to-south spread down the Pacific coastline. One human virus and nine marine mammal viruses in Chile had the rare PB2 D701N mammalian-adaptation mutation and clustered phylogenetically despite being sampled 5…

• DO
  Division of Intramural Research, National Institute of Allergy and Infectious Diseases

  Awards: 75N93021C00014, 75N93021C00017