Mammal-to-mammal transmission of HPAIV among marine mammals
A new study published in Nature Communications discusses a significant outbreak of H5N1 highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b that emerged in Chile in December 2022. The outbreak caused substantial mortality among wild birds, poultry, and marine mammals and included one confirmed human case. A comprehensive surveillance effort was conducted, involving the collection of over 18,500 samples from 9,745 cases, with 7.33% testing positive for HPAIV H5N1.
The HPAIV H5N1 virus exhibited rapid north-to-south dissemination along the Pacific coastline and was genetically linked to earlier outbreaks in Peru. Notably, key mutations, such as PB2 D701N, were identified in both marine mammals and the human case in Chile, suggesting potential adaptations for mammalian transmission.
The study provides evidence supporting sustained mammal-to-mammal transmission of HPAIV among marine mammals over considerable distances, as indicated by the phylogenetic clustering of viral genomes sampled across wide geographic spans within Chile.
