The deadly H5N1 bird flu virus has caused the first confirmed deaths of wildlife in Antarctica, with more than 50 skuas dying after being infected with the virus during the summer of 2023 and 2024. The research, led by Erasmus Medical Center in the Netherlands and the University of California, Davis, was recently published in the journal Scientific Reports and marks the first time that this highly pathogenic avian influenza virus has been confirmed to cause large-scale deaths of wildlife on the Antarctic continent.
The skua is a large brown seabird in the same family as the gull that lives mainly in polar and subpolar regions. As predators and scavengers, they play an important role in the ecosystem similar to birds of prey, but this scavenging habit may also increase their access to infected carcasses, potentially facilitating the spread of the virus in Antarctica. Earlier in 2024, scientists had detected H5N1 viruses in dead seagulls and skuas in January and February, but avian influenza had not yet been confirmed as the cause of their deaths. "We know there are animals infected with the virus, but this is the first study to demonstrate that they died from viral infection," said study co-senior author Ralph Vanstrels, a wildlife veterinarian at UC Davis Health. "That's an important distinction early in the outbreak."
In March 2024, the research team traveled to Antarctica just after the skuas and penguin breeding seasons ended. They examined wildlife at 10 sites in the South Shetland Islands, the northern Weddell Sea and the Antarctic Peninsula. When they encountered sick or dead animals, they collected tissue and environmental samples and performed necropsies to determine the cause of death. The team examined gentoo penguins, Adélie penguins and Antarctic fur seals but did not confirm that H5N1 was the cause of death in these animals. "As the expedition progressed, it quickly became apparent that skuas were the main victims," Van Strells said.
The research team detected the H5N1 virus in skuas at three locations: Hope Bay, Alcatraz Island and Beak Island. Among them, a mass mortality event of Antarctic skuas occurred on Beak Island. "We confirmed that highly pathogenic avian influenza was the cause of almost all deaths of skuas on Beak Island," said Matteo Jervolino, first author of the study and a doctoral candidate at Erasmus Medical Center in the Netherlands. "There, I saw first-hand the impact this virus can have on these populations." Van Strels described the situation as a "crisis of animal suffering." The virus attacks the brain, causing neurological symptoms such as neck twisting and abnormal stretching movements. Infected birds may walk or swim in circles, bump into objects, or fall from the air. Researchers stress that human activities contributed to the emergence of the virus and that humans also play an important role in limiting its spread.
The H5N1 virus was first discovered in a poultry and goose farm in southeastern China in 1996. It spread unchecked among poultry for several years, during which time it spread to wild birds and spread to Europe, the Middle East and Africa, later reaching North and South America and arriving in Antarctica by early 2024. The strain of the virus affecting Antarctic skuas has previously caused severe losses among elephant seals and sea lions in Argentina. The virus has also killed more than 400 million poultry and infected cows, mink, foxes, bears, otters, and many other mammals and wild birds. The virus can also infect humans, killing about half of the roughly 1,000 reported human cases. "When the virus first emerged in the poultry industry, we let it slip through our fingers. Once it entered wild bird populations, we lost the ability to control the virus. Now it has established itself in wild bird populations on every continent in the world except Oceania," said Tess Quicken, professor at the Erasmus Medical Center and corresponding senior author of the study.
Antarctic wildlife already faces extreme conditions and increasing pressures such as climate change, expanding tourism, invasive species, overfishing and pollution. The emergence of avian influenza represents another serious threat. Researchers stress the need for increased surveillance and monitoring to reduce the risk of further spread. Reliable population data are also limited. The last census of Antarctic skuas was conducted in the 1980s, when scientists counted about 800 breeding pairs. Without updated data, it's difficult to determine how significant the loss of 50 birds might be. "Every indication is that this virus will spread further," Quicken said. "If no one is paying attention, we won't know what's going on."