Detection and spread of high pathogenicity avian influenza virus H5N1 in the Antarctic Region

Abstract

The Antarctic is the only major geographical region in which high pathogenicity avian influenza virus (HPAIV) has never previously been detected. The current panzootic of H5N1 HPAIV has decimated wild bird populations across Europe, North America and South America. Here we report on the emergence of clade 2.3.4.4b H5N1 HPAIV in the Antarctic and sub-Antarctic regions of South Georgia and the Falkland Islands respectively. We initially detected H5N1 HPAIV in samples collected from brown skuas at Bird Island, South Georgia on 8thOctober 2023. Since this detection, increased mortalities were observed in brown skuas, kelp gulls, elephant seals and fur seal at multiple sites across South Georgia. We confirmed H5N1 HPAIV in multiple brown skuas and kelp gulls across four different sampling locations in South Georgia. Simultaneously, we also confirmed H5N1 HPAIV in a southern fulmar in the Falkland Islands. Genetic assessment of the virus indicates spread from South America, likely through movement of migratory birds. Here we describe the emergence, species impact and genetic composition of the virus and propose both introductory routes and potential long-term impact on avian and mammalian species across the Antarctic region.

Catastrophic mortality of southern elephant seals caused by H5N1 avian influenza

“…Satellite tracks and flipper tagging data confirm the connection between these sites (Campagna et al, 2020;Lewis et al, 2006). Evidence so far indicates that the virus reached South Georgia Island (Bennison et al, 2023).…”

Unexpected delayed incursion of highly pathogenic avian influenza H5N1 (clade 2.3.4.4b) in the Antarctic region

“…This is in contrast to the seabird breeding season 2023/24. In October 2023 the first confirmed H5N1 cases were detected on the Falkland (Malvinas) Islands, and in November on South Georgia Island in the sub-Antarctic 10,12 (Figure 1). Given the overlap of species breeding and migrating via the Falkland Island and South Georgia towards the Antarctic Peninsula and its offshore Islands (e.g., the South Shetland Islands), researchers in the region and the tourist industry have been very diligent in identifying unusual bird behaviour and mortality events.…”

“…are known scavengers (Figure 2), leading to high risks of exposure to HPAIV via the consumption of infected carcasses. It is thus no surprise that Brown skuas where often among the first confirmed cases both on South Georgia and the Antarctic Peninsula 10 . This species, which can be observed at shorelines of South America, the Falkland Islands and South Georgia 13 , is likely to be an important player in spreading the virus.…”

“…In addition, locations of confirmed cases of infection in 2023/24 (left) are included. Numbers refer to the following references, (a) technical annex, (b) 10 , (c, e) 11 , (d, f) 12 . Maps created with Natural Earth.…”

Avian influenza overview September–December 2023

“…They all belong to the B3.2 genotype, a reassortant of the original Eurasian A(H5N1) virus introduced into North America in late 2021, and local North American avian influenza viruses (FluGlobalNet, online). Bennison et al (2023) outlined that discrete trait analysis based upon the country of origin suggested that the source of HPAI virus for both South Georgia and the Falkland Islands was Chile. In Asia, Cambodia reported outbreaks of HPAI A(H5N1) to WOAH from a region where human cases of A(H5N1) belonging to clade 2.3.2.1c have occurred (KhmerTimes, online).…”