ITHACA, N.Y. - Migrating birds that breed in the Arctic are spreading avian influenza to polar bears in eastern Greenland, according to a new Cornell University study that found evidence of infections in bear blood samples acquired from Greenland Inuit subsistence hunters.
Polar bears that hunt on dwindling sea ice are being forced to search for food elsewhere, which has likely increased their odds of exposure to highly pathogenic avian influenza (HPAI).
“With climate change, we know that the bears are changing their diets, and they’re likely becoming exposed to many new pathogens on land that they could be naïve to, because they come from a life highly adapted to the ice,” said Kayla Buhler , a postdoctoral fellow in the College of Veterinary Medicine. Buhler is first author of the study, published in Emerging Infectious Diseases .
A wide range of global bird species migrate northward via East Atlantic and North American Atlantic flyways to breed in the Arctic and Greenland. There, they congregate in large colonies, creating a perfect hot spot for viral mixing and transmission.
“It’s important for us to monitor what new pathogens are becoming established in polar bears because we don’t know how they’ll be affected,” said Buhler, who is also a researcher at the University of Inland Norway. “As populations become more and more stressed, diseases and pathogens could play a critical role in conservation efforts.”
Samples from polar bears in this study were collected during the subsistence hunts that occur around Scoresby Sound, also known as Ittoqqortoormiit in the Eastern Greenlandic dialect.
Disease can spread when bears eat birds and eggs, or seals or other animals infected with HPAI. Polar bears with an active infection could potentially pass avian influenza to other bears when they congregate at hunting carcass sites and at dumpsters near human settlements.
In 2026, in Svalbard, scientists reported a young polar bear died from HPAI after eating an infected walrus. A 2025 study in Svalbard detected H5N5 avian influenza virus in Arctic foxes, which scavenge and prey on birds and eggs. Both studies reported viruses with mutations suspected of making the virus more likely to infect mammals. And dead birds in Greenland have been found with strains of HPAI, including H5N1 and H5N5.
In the current paper, co-authors from Aarhus University, Denmark, acquired a total of 109 heart blood samples between 2016 and 2025 from Inuit hunters, with whom they collaborate regularly.
Out of the 10 years of samples, there was no evidence of any infection until 2024, when the scientists detected antibodies for influenza A in 21% of 14 bears. By 2025, the rate had gone up even more; they found antibodies in 43% of 14 bears. Further testing identified four positive bears with specific antibodies for HPAI viruses.
“We’re not detecting active infections; we’re detecting a prior infection that has been cleared by the animal,” Buhler said. “This is one of the first studies to show that bears can recover and do quite well after infection.”
The bears that were exposed to virus likely contracted it during the summer, while subsistence harvests took place the following spring. The hunters, who have extensive traditional knowledge of the bears, have not observed sick animals.
For additional information, read this Cornell Chronicle story.
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Emerging Infectious Diseases