H5N1 bird flu and Antarctica: a deadly threat to wildlife

A deadly animal pandemic is on the verge of spreading worldwide.

Scientists have formally recorded highly pathogenic avian influenza virus (HPAIV) in several bird and mammal species in the Antarctic, the planet’s most remote region. Until now, this icy refuge had never faced such a lethal strain.

Since 2021, H5N1 clade 2.3.4.4b has devastated wild bird and mammal populations across the globe, spreading rapidly from Europe to North America and then south into South America. Genetic analysis suggests the virus is beginning to enter the Antarctic region, most likely carried south by migrating birds.

Researchers have feared this moment for years. The region’s iconic species, including penguins and albatrosses, face an existential crisis.

"Antarctica and the sub-Antarctic islands possess unique ecosystems which support the population strongholds of several avian and marine mammal species," write the authors of the recent paper, based on British Antarctic Survey (BAS) data.

"High mortality disease outbreaks therefore represent a substantial threat to already vulnerable seabird populations."

H5N1 bird flu reaches South Georgia

The first sign came on 17 September 2023, when BAS researchers on the South Georgia Islands, roughly halfway between Argentina and Antarctica, saw a giant petrel twitching and having difficulty moving.

Brown skuas fed on the bird’s body after it died. By 8 October, they had also begun twitching. Two days later, researchers recorded the largest number of bird deaths ever documented among non-breeding birds on the islands.

By early December, southern elephant seal and Antarctic fur seal colonies were showing signs of illness, with animals coughing, struggling to breathe and taking short, sharp breaths.

Between 8 October and 9 December, researchers counted 33 bird carcasses and 17 mammal carcasses across eight sites around the South Georgia Islands. Around 66% tested positive for HPAIV H5N1.

On the nearby Falkland Islands, which lie closer to Argentina in the subantarctic region, two further bird species tested positive: black-browed albatrosses and southern fulmars.

Suspected cases on the Antarctic mainland

The virus has not yet officially reached the Antarctic mainland, although some researchers on the western peninsula believe the animal pandemic is already present on the remote continent.

In March 2024, an international team submitted a study, prior to peer review, on suspected H5N1 cases in Adélie penguins and Antarctic shags "at the southernmost latitude so far in Antarctica".

The team detected the virus at two breeding sites on the Antarctic Peninsula and the west Antarctic coast between December 2023 and January 2024.

Should those findings be verified, Australia would be the only continent without this bird flu strain. There is also no known spread in the wider Oceania region.

The threat to Antarctic wildlife

The continuing animal pandemic has been "particularly severe" in South America, Banyard and her colleagues explain, causing mass deaths among birds and marine mammals.

Unlike wildlife elsewhere in the world, South American wildlife has not encountered a highly pathogenic avian virus in recent history. Infection has killed as many as 40% of the population in some species.

The tragedy highlights the "extensive ecological impact of HPAIV and the ongoing threat it presents to naïve hosts," the authors say.

For some isolated Antarctic species, that threat could be a final blow. Antarctic fur seal numbers on Bird Island are already falling severely, while mainland penguin colonies are suffering catastrophic losses.

A pandemic arriving on their doorstep is the last thing these birds and mammals need.

The study was published in Nature Communications.