Some polar bears are surviving bird flu, and scientists want to know why

Researchers have found antibodies to H5 bird flu in four polar bears in East Greenland. All four looked healthy when hunters took them. The antibodies point to infections the animals had already cleared. Kayla Buhler led the study. She works at the University of Inland Norway and holds a postdoctoral post in the veterinary college at Cornell University. The work appears in the journal Emerging Infectious Diseases.

Inuit hunters near Scoresby Sound helped gather the samples. With Aarhus University in Denmark, including the researcher Christian Sonne, they took heart blood from 109 bears across 2016 to 2025. All samples came from the hunting season between January and May, under annual government quotas. Every sampled bear appeared healthy, and the hunters had not reported seeing sick ones.

A first test looked for antibodies to the wider influenza family. None of the 81 bears sampled up to 2023 was positive. Three of 14 bears were positive in 2024, and six of 14 in 2025. Not all nine were specific to H5. Further tests at the National Microbiology Laboratory in Canada found H5-linked antibodies in four bears, all sampled in 2025.

The study did not establish how the bears were exposed. The team considers eating infected birds or mammals a likely route. Glaucous gulls move between East Greenland and Svalbard, and H5 viruses have repeatedly been found in gulls on Svalbard. Bird flu has already been reported to have killed polar bears in Alaska and on Svalbard. Buhler said bears on Svalbard now take down reindeer and raid bird colonies. The researchers did not show that sea ice loss caused the infections. They suspect the bears met the virus in the previous summer or autumn.

Antibodies cannot show the timing of an infection or how sick a bear became. Only 14 bears were tested in each of the last two years, all from one hunting area. The study cannot say whether surviving once protects a bear from a second infection. The team wants to learn whether Greenland viruses have mutations that favour infection of mammals, and whether the virus spreads between bears that gather at carcasses.

Correction, 31 October 2026: an earlier version said hunters reported that each bear looked healthy. The source says every sampled bear appeared healthy and the hunters had not reported seeing sick ones.

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