Bird flu spreads to mammals in Antarctica: Australian researchers alarmed

Antarctica/Sydney. The crabeater seals doze peacefully in the Antarctic sunlight, unaware that a deadly enemy is already raging among them. A killer virus that has reached the most remote corners of the planet is now jumping from animal to animal, leaving death and devastation in its wake.

So far, 15 animal species in the region have been confirmed to have the H5N1 avian influenza virus—including seabirds, penguins, and, worryingly, seals. "We now definitely have evidence in most Antarctic seal species," Australian researcher Meagan Dewar, who recently returned from her fourth expedition this year, told Australian broadcaster ABC . "Other teams found that Antarctic fur seals and elephant seals are severely affected, crabeater seals and Weddell seals have also died, and some leopard seals have also been detected."

Particularly worrying: The pathogen, which was introduced from South America via carrion birds in 2023, appears to be behaving differently than expected. Initially, the researcher thought she would see "hundreds, if not thousands, of dead penguins" – but that wasn't the case. Viral ecologist Michelle Wille confirms this: "In the Antarctic and sub-Antarctic, we've so far seen mainly deaths in brown and South Pole skuas, while only a few infections or deaths have been detected in other species such as penguins," she wrote in an email. Unfortunately, this also poses the risk that penguins could be asymptomatic carriers.

The virus ecologist also reported on the sometimes frightening effects on the birds. The virus attacks the animals' brains, causing them to exhibit neurological symptoms such as coordination problems and the inability to stand up. "We also see shortness of breath," Wille wrote. In some species, inflammation of the eyes and other changes to the eyes have also been observed. Many birds die painfully.

Gentoo penguins affected by HPAI H5N1 avian influenza in the Falkland Islands.

Source: IMAGO/Danita Delimont

Using the same molecular tools used in the fight against COVID-19, Wille is currently examining hundreds of samples from skuas, penguins, and seals at the WHO Collaborating Centre for Influenza in Melbourne. The analyses are intended to reveal where and how the highly pathogenic H5N1 is spreading on the Antarctic continent. Initial results indicate that the virus is present in the same locations as last year—but there are also reports of cases far from the original source of infection, demonstrating that the pathogen is spreading.

Avian flu has already reached the sub-Antarctic Crozet and Kerguelen Islands, over 7,000 kilometers from its origin in the South Georgia Islands. French researchers reported "unprecedented and alarming mortality rates among southern elephant seals" there at the end of 2024; king penguins, gentoo penguins, and brown skuas were also among the victims.

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From Kerguelen, it's less than 500 kilometers to Australia's remote Heard and McDonald Islands, a hotspot for biodiversity and potentially new hosts. If the virus makes this leap, the next step could lead directly to the Australian mainland. "There are many areas where we simply don't know whether avian influenza has arrived yet—and if so, to what extent," Dewar told the Australian broadcaster.

Danger also threatens from the north: Migratory birds returning from the northern hemisphere spring could bring the virus with them from H5N1 hotspots. The disease has "catastrophic effects on wildlife worldwide," says Wille. For example, one-third of all gannets worldwide have died from it. For wildlife in the Antarctic and sub-Antarctic, the highly pathogenic H5N1 virus poses a "very real threat." Furthermore, her research suggests that an introduction to Australia is no longer a question of "if," but only "when."

Particularly worrying is what could happen if the pathogen encounters Australia's endemic animal species: marsupials like koalas and kangaroos, or marine mammals like the Australian fur seal. Experts already fear that endangered species could be wiped out.

In addition to the ecological consequences, there is also a risk to humans. According to the WHO, 112 human infections have been reported worldwide since 2020, including an Australian toddler who became infected in India but recovered. Most cases have recently occurred in the USA, where the virus is spreading among cattle. While the WHO currently considers the risk to the general population to be low, with each mammal-to-mammal transmission, the likelihood increases that the virus will become more adaptable to mammals—and thus also to humans.