Bird flu reaches the Antarctic region 

Seals laying on Antarctic ice

Avian Influenza has, for the first time, been recorded in a previously untouched region—Antarctica. This poses threats to species that have never encountered the virus before. Image credits: Robert Haverly via Unsplash

The first known cases of Highly Pathogenic Avian Influenza (HPAI) in the Antarctic region have been recorded, sparking concern for the vulnerable penguin, seabird, and seal populations. A recent announcement from the British Antarctic Survey confirmed that two brown skuas Stercorarius antarcticus on Bird Island (South Georgia) tested positive for HPAI, making them the first cases of this lethal bird flu in the region. HPAI viruses were first identified 64 years ago but this latest outbreak of HPAI has caused mass mortalities in wild birds since its emergence in 2021, and has even recently been recorded in mammals. This latest spread to the Antarctic region leaves Oceania as the only continent free from HPAI.  

The first known cases of Highly Pathogenic Avian Influenza (HPAI) in the Antarctic region have been recorded.

Avian influenza is a type A group of influenza viruses that predominantly infects birds, which across its diversity of sub-types can infect both humans and other animals. Strains are named according to the numbered sub-type of two virus surface proteins: haemagglutinin (H) and neuraminidase (N). The current Highly Pathogenic Avian Influenza virus circulating is the bird-adapted HPAI A(H5N1) virus. 

Pathogenicity is a pathogen’s ability to cause disease, influenced among other factors by how transmissible it is, and the effect it has on a host. Low Pathogenic Avian Influenza (LPAI) circulates at low levels with limited impact in wild bird populations, reaching poultry populations after being introduced by migratory birds. Mutations to low pathogenic viruses can lead to highly pathogenic strains emerging in the densely populated environments of poultry farms, with disastrous impacts on poultry and farmers, before escaping to wild bird populations with devastating consequences.  

Unlike LPAI, highly pathogenic strains have much greater disease-causing potential; they cause respiratory and neurological symptoms and very high mortality, causing some colonies of affected birds in the UK to halve in size.  

Brown skuas—the first birds to test positive for the virus in South Georgia—are large predatory and scavenging seabirds, with these feeding habits offering an infection pathway through eating infected birds or mammals. These birds spend the non-breeding season off the coast of South America where there have been hundreds of thousands of cases of HPAI, and it is likely that brown skuas brought the disease with them on their migration back to the Antarctic region.  

The spread of HPAI to the Antarctic region is concerning because the area contains many endangered and endemic species, which have never been exposed to HPAI and therefore lack pre-existing immunity. The authors of a risk assessment report released by the SCAR Antarctic Wildlife Health Network in September warned that HPAI could have a “devastating impact” on many Antarctic species. The report identified animals that could predate or scavenge infected birds as those at high risk from HPAI (fur seals, sea lions, skuas, and gulls), with penguins and other colonial species also at risk due to disease spread through direct contact with infected individuals, and high concentrations of droppings. Some mobile seabird species (including brown skuas and southern giant petrels) could also act as disease vectors, carrying HPAI to other Antarctic islands or to the Antarctic mainland—1500 km away from Bird Island, the location of these first cases. 

The authors of a risk assessment report released by the SCAR Antarctic Wildlife Health Network in September warned that HPAI could have a “devastating impact” on many Antarctic species.

Bird Island is a wildlife haven, supporting a range of seabird populations—many of which are threatened or endangered—as well as 50,000 pairs of penguins and 65,000 pairs of fur seals. It is also home to a team of Antarctic scientists who could carry the virus on shoes or equipment and for whom HPAI poses a potential health threat. Alongside pre-existing biosecurity steps, some enhanced hygiene measures had already been introduced in anticipation of HPAI’s spread to the region. Since these first cases, measures have been stepped up, with fieldwork requiring contact with animals suspended for the safety of both the island’s wildlife and researchers.  

Although there are many uncertainties regarding the spread and severity of HPAI in the Antarctic, this latest risk compounds the pressures on this fragile environment and its inhabitants. Disease can interact with other stressors, including plastic pollution, whilst climate change-induced loss of sea ice this year has caused catastrophic breeding failures for emperor penguins. The slow-breeding strategies of seabirds and penguins (often one chick per year, with several non-breeding years) leaves them vulnerable to extinction in the face of disturbances, as it takes longer for populations to bounce back. The effects of a disease as lethal as HPAI could be devastating for the unique fauna of the Antarctic. Nevertheless, there is a glimmer of hope as recent research has found some evidence of recovery from and immunity to HPAI in a small sample of UK seabird species, offering a potential route for populations to persist.