Transcontinental Spread of HPAI H5N1 from South America to Antarctica via Avian Vectors

During China's 41st Antarctic research expedition, samples were collected from wildlife on the Fildes Peninsula, South Shetland Islands, Antarctica. Real-time RT-PCR screening confirmed H5N1 positivity, representing the first identification of the virus in brown skuas on the Fildes Peninsula. Whole-genome sequences obtained from positive samples via next-generation sequencing were subjected to phylogenetic and phylogeographic analyses. The results revealed that these Antarctic strains are most closely related to H5N1 viruses circulating in South America, particularly from Peru and Chile, suggesting a likely introduction via avian migration routes. Furthermore, a unique 17-amino-acid deletion was identified in the stalk region of the neuraminidase (NA) gene, which is uncommon among globally sampled clade 2.3.4.4b variants. This study confirms the arrival of HPAI H5N1 in the Antarctic continent and underscores the necessity for enhanced surveillance to understand the viral ecology and potential risks within this unique ecosystem.