Detection and Spread of High Pathogenicity Avian Influenza Virus in the Antarctic Region

Few infectious diseases have such a rapid and devastating global impact as Avian Influenza virus (AIV). AIVs exist as a vast spectrum of subtypes with importance generally attributed according to impact upon kept birds. AIV H5 viruses and H7 subtypes are of most significance due to their historic impact upon poultry although they can also pose zoonotic risk and as such are of interest to both animal and human health sectors wherever they emerge.  Among the various H5 viruses that circulate, those within the Goose/Guandong lineage that have emerged from a virus firstly detected in China in 1996 (the A/goose/Guangdong/1/96-lineage) are of highest importance due to the devastating outbreaks and lethality birds, terrestrial and marine mammals and occasionally humans. 
 
In recent years, HPAIV has spread globally through unprecedented epizootic waves, first in the Eurasia during 2020-2021 before transatlantic spread to North America and onward dissemination into South America. This worldwide progression has been driven by migratory wild bird species with avian and mammalian mass die-offs reported as far south as Patagonia. By autumn 2023, it was evident that this spread would not stop at the Americas: field evidence suggested that an intercontinental jump to Antarctica was imminent.
 
The World Organisation for Animal Health (WOAH) and Food and Agriculture Organisation (FAO) International Reference Laboratory for Avian Influenza, Swine Influenza and Newcastle Disease virus at the Animal and Plant Health Agency (APHA), Weybridge, UK, fosters international linkages as part of threat definition for emerging viruses. Collaboration and support extend to all British Overseas Territories including the Falkland Islands (FI), South Georgia and the South Sandwich Islands (SGSSI), and the British Antarctic Territories (BAT), primarily through collaboration with the research stations run by the British Antarctic Survey (BAS) but also through governmental linkages. Our responsibilities in these regions include disease control to protect livestock and wild species, assessment of zoonotic risk and supporting research activities in these remote locations.
 
The fragile ecosystem on these islands, alongside the importance of high-profile conservation species means that by working closely with BAS and the local governments we have been able to support rapid diagnosis to define risk in the area as the virus emerged through migratory pathways. These locations host a unique wildlife population, including endangered and charismatic avian and marine mammal species. Additionally, the severe seal casualties reported in South America due to the HPAI epizootic raised concerns about the potential mammalian adaptation of the original avian virus, which could increase the potential risk to humans.
 
While AI has frequently made headlines for its catastrophic effects on the poultry industry, the recent panzootic has demonstrated the profound effect on wildlife. AIV is a virus that infects, mutates, and thrives in different wild birds (historically Anatidae and seabirds) and the ability of these viruses to exchange genetic material following co-infection (reassortment) means that the emergence of novel viruses can have a profound effect on infection dynamics, including infection of different species. This underscores the importance of understanding and mitigating the effect of this pathogen through its wild reservoirs, whose ecology and ethology greatly influence viral evolution. 
 
However, research in this field is often restricted by limited financial resources and the considerably challenging conditions under which these activities must occur. These locations are difficult and expensive to reach, and sampling often requires the trapping and handling of wild animals. There are health and safety concerns for scientists, and environmental conditions can affect the consistency and repeatability of research activities. The timely collection of data and findings in our study has been made possible through collaboration between several British institutions, including BAS, the governments of the FI and SGSSI, and our IRL team at APHA Weybridge. Support from the UK government (Department for Environment, Food and Rural Affairs and devolved administrations), the Royal Navy, the Royal Air Force, and local cruising and fishing vessels has also been crucial. Partners have shared resources (both financial and personnel) and knowledge to track and document this distressing event. This research owes much to the goodwill of volunteers and professionals, including biologists, veterinarians, environmentalists, ecologists, policy experts, virologists, and molecular biologists, many of whom have travelled from the UK to work in these remote locations to define the threat of this virus to both animal and human health. 
 
Our study reports the first detection of clade 2.3.4.4b H5N1 HPAI in the Antarctic and Sub-Antarctic regions. We initially detected H5N1 HPAIV in samples from brown skuas (Stercorarius antarcticus) at Bird Island, on South Georgia, on October 8, 2023. Almost simultaneously, we confirmed H5N1 HPAIV in southern fulmars (Fulmarus glacialoides) and black-browed albatrosses (Thalassarche melanophris) in the FIs. Since then, mortalities have been observed in several avian and mammalian species at multiple sites across these archipelagos. H5N1 HPAIV was confirmed across several sampling locations in multiple avian species and two seal species, including Brown Skuas, Kelp gulls (Larus dominicanus), Antarctic tern (Sterna vittate), South Georgia shag (Leucocarbo georgianus), Southern elephant seals (Mirounga leonine) and Antarctic Fur Seals (Arctocephalus gazella). A key collaborative linkage enabled by many of the institutions mentioned above allowed APHA senior scientist, Dr Marco Falchieri, to travel to the region, sample carcasses and train staff both on location and virtually in safe sampling techniques. 
 
A critical feature of the work was being able to reassure the research teams working on the islands on the zoonotic risk of infection. Samples from seal carcasses were expedited for genetic assessment. Genetic analysis of the virus indicates a spread from South America, likely through migratory birds. Importantly, genetic assessment of sequences from mammalian species demonstrated no increased risk to human populations beyond what had been observed in other instances of mammalian infections globally.
 
We are continuing to work closely with the teams on the islands to monitor the situation, conscious of the fact that alongside introduction of virus through migratory bird pathways, environmental contamination in the form of frozen carcasses, may pose a risk for future disease events. We continue to engage with the governmental and research communities in the area to monitor and sample populations going forward.