The World Health Organization called Friday for expanded surveillance of H5N1 avian influenza in Arctic mammals after researchers confirmed that four Greenland polar bears carried antibodies to the virus. The finding signals wider spread into previously unaffected wildlife populations.

The antibody detections suggest the bears were exposed through scavenging infected seabirds or marine mammals. Polar bears had not previously been documented as carrying the pathogen in Greenland.

A WHO spokesperson said the agency was coordinating with Danish and Greenlandic health authorities to assess the risk to Arctic communities and wildlife. The US Centers for Disease Control and Prevention has repeatedly warned that each mammalian spillover raises the chance of viral mutations enabling mammal-to-mammal transmission.

Scientists have tracked H5N1's expanding host range since 2022, when the clade 2.3.4.4b strain began infecting foxes, seals, sea lions and dairy cattle. Researchers at the European Food Safety Authority have described the Arctic as an emerging reservoir where migratory birds carry the virus across continents.

The WHO reiterated that the current public health risk to the general population remains low. The organization urged governments to strengthen monitoring and report unusual wildlife deaths promptly.