A new kind of death is coming to Antarctica, scientists fear. The harsh environment is full of everyday heartbreak: predation, starvation, chicks that are lost at sea when their icy shoreline melts away. Now a novel pathogen threatens to rip through colonies of marine mammals and birds, potentially including penguins. If the very worst happens, it could make ghosts of entire species—and scientists can’t do much more than wait.

A deadly strain of H5N1 avian influenza has been blazing through poultry farms and flocks of wild birds around the world, infecting mammals and even killing at least one polar bear. Now it’s knocking at the gates of Antarctica, just as dozens of species that have likely never experienced any strain of avian influenza are congregating to raise their next generation. Avian influenza is currently causing big outbreaks on islands around the southern tip of South America, about 1,000 miles from the Antarctic Peninsula. The virus has led to clusters of illness in Gentoo Penguins on the Falkland Islands in January and in fur seals, elephant seals and other animals on the island of South Georgia last December. Scientists fear it will just require a short jump for the virus to hit the Antarctic Peninsula and spread into the rest of the continent.

“We’re kind of braced for impact. We’ve been like that since basically the end of [last] year,” says Marcela Uhart, a wildlife veterinarian at the University of California, Davis, who is currently monitoring the outbreak from Patagonia. “It is unlikely that [avian influenza] will not get there just because of how connected the species are,” with the animals often traveling long distances through the Southern Ocean to find food.

On supporting science journalism

If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Avian influenzas come in two varieties. Typically, wild birds catch mild cases of what scientists call “low-pathogenicity” flu, whereas farmed poultry species such as chickens and ducks can develop much more serious infections with “high-pathogenicity” strains. These different flavors can mix, creating more infectious viruses such as the one currently ravaging South America. That combination, a substrain called clade 2.3.4.4b that developed within the past decade, comes from a lineage identified in China in the mid-1990s that has led to occasional outbreaks around the world. But clade 2.3.4.4b has now become a Frankenstein virus that combines the severe disease of poultry strains with a particular affinity for infecting wild birds. In addition to hitting South America, the virus has devastated seabird colonies in Europe, followed migratory birds south into Africa and jumped the Atlantic Ocean to infect even the regal California Condor.

“Avian influenza is nothing new; it’s been around for a very, very long time,” says Christian Walzer, a wildlife veterinarian and executive director of health at the global conservation organization Wildlife Conservation Society. But this avian influenza is different. “What’s important to understand is that the whole dynamics have changed,” he says.

Despite the rapid spread of this strain, scientists aren’t sure how it is transmitted between animals, particularly how it spreads between birds and mammals. Many infected species are scavengers, suggesting that consumption of infected corpses could contribute to transmission; healthy animals may also pick up the virus from the feces of infected ones, researchers say. Some species seem to be resistant to sickness, although they could still be contributing to transmission. “The big problem we have is: we don’t really understand how some birds are able to be infected with this virus and not get sick, but it’s clear that that does happen,” says Ashley Banyard, a virologist at the U.K.’s Animal and Plant Health Agency.

By late 2022 and into 2023, the brutal clade 2.3.4.4b virus in South America had killed at least about 600,000 birds and 50,000 mammals—and likely many more, scientists say. “We’ve never had anything of this magnitude in the Southern Hemisphere,” Uhart says.

Antarctica and Australia are currently the only continents this avian influenza has yet to reach—as far as scientists can tell. For Antarctica in particular, the virus may simply be spreading undetected. “There is no way to know for sure,” says Michelle Wille, a viral ecologist at the University of Melbourne in Australia, who focuses on avian viruses. “One of the great challenges is that it could already be there, in a place where few people visit.”

Detecting any wildlife infection in a remote location is difficult work, but that’s particularly true when most victims are ocean-based species. “It’s really hard to detect anything at sea,” says Amandine Gamble, an ecologist at Cornell University. “It’s probably a huge underestimate of the actual number of fatalities.”

Scientists are worried that if the virus takes hold in Antarctica, casualties on the continent could be particularly high. “Highly pathogenic avian influenza has never been recorded there before,” says Thijs Kuiken, a pathologist at the Erasmus University Medical Center in the Netherlands. “The majority of the 48 species of birds and 26 species of marine mammals present in Antarctica are likely susceptible to infection and disease from this virus.”

Not only are these animals immunologically vulnerable, but they also have lifestyles that put them at additional risk of infection. “You have these massive, densely packed together bird colonies and some of those megacharismatic, highly threatened species, which are all packed together down there,” such as penguins, Walzer says. “If [the virus] does hit, the impacts will be potentially really devastating.”

“Entire populations may disappear,” Wille says of a potential Antarctic outbreak. “This would be a catastrophe.”

It could be a catastrophe for species beyond those directly affected—and even beyond those that call Antarctica home, Uhart says. For instance, if there are mass die-offs on the continent, and these corpses become encased in ice rather than sink into the ocean, the deaths could potentially affect the global carbon cycle and nutrient flow. “I don’t think anybody can even imagine what the loss of potentially this huge biomass of wildlife would mean for the ocean,” Uhart says. “I don’t think we understand what this means.”

Timing could influence just how bad an Antarctic avian influenza outbreak could be, experts say. Currently, the continent is at the peak of its summer, with many species still busy raising their young—whose fresh immune system could be more susceptible to avian influenza or more likely to spread it, scientists say. “Now is a critical stage,” Gamble says.

“If it actually reaches now, it can be very, very fast to spread,” she says. “If we manage to not have the virus reaching the Antarctic continent for a few more weeks, we might be safe for this year.” Most species will disperse out of tightly packed colonies until the next breeding season, making them less likely to encounter other animals—and therefore the virus. Still, Gamble and others worry that would likely be only a temporary stay, given how aggressively the virus is circulating globally. Antarctica may dodge the crisis this year, only to suffer during the next Southern Hemisphere spring and summer.

As with so many ecological disasters, the story of avian influenza highlights the consequences of human disruption of the natural world, scientists say. Modern poultry farming, where birds are packed even more tightly than the most crowded penguin colony, fosters the spread of disease. And although several avian influenza vaccines exist, countries around the world have typically opted to instead kill any farm’s entire population after exposure. Tens of millions of chickens have died or been culled in the U.S. alone since 2022. That decision has been driven by fears that vaccinated chickens would interfere with international trade because tests can’t distinguish between infected and vaccinated birds. Nations that don’t vaccinate won’t import poultry with a positive avian flu test.

And now, Uhart says, it’s sea lions and elephant seals, cormorants and pelicans and, yes, even penguins that are suffering from this vicious virus. “These poor animals are dying without a voice,” she says. “Unless we tell their story, it could very well go untold.”