Blood samples from four polar bears in eastern Greenland showed antibodies associated with highly pathogenic bird flu, adding evidence that Arctic wildlife is encountering viruses carried through the region by migrating birds.
The finding comes from research published Oct. 13 in Emerging Infectious Diseases. First author Kayla Buhler is a postdoctoral fellow at Cornell University’s K. Lisa Yang Center for Wildlife Health and a researcher at the University of Inland Norway.
The study examined 109 plasma samples collected from 2016 through 2025. The blood came from polar bears harvested by Inuit subsistence hunters near Scoresby Sound, also called Ittoqqortoormiit, in East Greenland.
Researchers found no influenza A antibodies in samples collected before 2024. Three of 14 bears sampled in 2024 had those antibodies, or 21%. In 2025, six of 14 tested bears had influenza A antibodies, or 43%.
Further testing found antibodies matching highly pathogenic H5 viruses in four of the bears sampled in 2025. Influenza A screening covers a broader group of viruses; the follow-up tests supplied the more specific evidence of exposure to the highly pathogenic lineage.
Antibodies point to prior exposure
The samples came from bears that appeared healthy during the January-through-May hunting season. Hunters reported no clinical signs of illness.
Antibodies show that an animal’s immune system has encountered a virus. The findings were consistent with bears surviving after exposure, rather than documenting active infections when the blood was collected.
The small annual samples also produced broad uncertainty ranges. The study reported a 95% confidence interval of 8% to 48% for the 2024 result and 21% to 67% for 2025.
Researchers first screened the samples for influenza A antibodies, then examined nine positive samples and three negative samples with a second laboratory test using representative H5 and H7 viruses.
Four 2025 samples reacted to H5N1 viruses in clade 2.3.4.4b, a highly pathogenic avian influenza lineage. The authors said reactions with some other H5 viruses are possible, but the pattern of results strongly supported exposure to that lineage.
Migrating birds are a likely source
Greenland connects the East Atlantic and North American Atlantic bird migration routes. Shorebirds and waterfowl gather in large Arctic breeding colonies, creating opportunities for viruses to circulate and mix.
The researchers believe the bears were probably exposed during summer or fall bird migration before the following spring’s harvest. Migrating birds are absent during the polar bear hunting season.
Possible routes include eating infected birds, eggs or mammals, scavenging carcasses, or contact with contaminated material. The study identifies eating infected or dead animals as the most likely route, while saying further research is needed to determine which pathways matter for polar bears.
The work also raises questions about whether viruses circulating in Greenland have changes that make them better able to infect mammals.
Bears can gather at carcasses and near human settlements, creating potential opportunities for transmission that researchers say need further investigation.
Sea ice loss changes feeding opportunities
The Arctic is warming faster than much of the planet, with the western Arctic warming at about four times the global rate, according to Cornell’s account of the research. Shrinking sea ice is pushing bears to look for food on land, increasing contact with animals and pathogens outside their ice-based hunting grounds.
Buhler said polar bears in Svalbard, Norway, have begun hunting reindeer and raiding bird colonies. She said changing diets could expose bears to pathogens they have little prior experience with.
A young polar bear in Svalbard was reported to have died from highly pathogenic avian influenza in 2026 after eating an infected walrus. Researchers also detected H5N5 in Arctic foxes there in 2025. Cornell said those reports involved viruses with mutations suspected of improving their ability to infect mammals.
Bird flu strains including H5N1 and H5N5 have also been detected in dead birds in Greenland. The new polar bear results fit that broader timeline of avian influenza moving through Arctic ecosystems.
Hunters help monitor remote wildlife
Scientists at Aarhus University in Denmark obtained the samples through ongoing work with Indigenous hunters. Greenland regulates subsistence hunting through annual quotas, and the researchers collected samples from animals already harvested under that system.
The team included scientists in Norway, Denmark and Canada, along with Buhler’s Cornell affiliation. The researchers said continued collaboration with local hunters could strengthen surveillance in places that are difficult to monitor.
Support came from Denmark’s Environmental Protection Agency, the European Union’s Horizon Europe program, the Morris Animal Foundation and Cornell’s K. Lisa Yang Center for Wildlife Health.
The authors said increased surveillance in Greenland could help provide early warning of bird flu moving through linked migration routes, while tracking how polar bears respond to emerging infections.
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