First case of deadly bird flu in polar bears reported in Alaska

The infected polar bear provides further evidence of how widespread this virus, a highly pathogenic form of H5N1, has become and how unprecedented its behavior has been. Since the virus emerged in 2020, it has spread to every continent except Australia. It has also infected an unusually wide variety of wild birds and mammalsincluding foxes, skunks, pumas and sea lions.

“The number of infected mammals continues to grow,” said Dr. Bob Gerlach, Alaska State Veterinarian.

In most cases, the virus has not caused mass die-offs in wild mammal populations. (South American sea lions have been one notable exception.) But it does represent a new threat to the already vulnerable polar bear, which is endangered by climate change and the loss of sea ice.

“The concern is that we don’t know the general extent of what the virus can do in polar bear species,” Dr. Gerlach said.

The polar bear was found dead last fall in the far north of Alaska, near Utqiagvik. Swabs collected from the animal initially tested negative for the virus. But when experts conducted a more comprehensive study, performing a necropsy and collecting tissue samples from the bear, they found clear signs of inflammation and disease, Dr. Gerlach said.

Last month, tissue samples from the bear. tested positive for the virus, according to the Alaska Department of Environmental Conservation. Ultimately, the virus was identified in multiple organs, Dr. Gerlach said. “I think it would be safe to say that he died from the virus,” he said.

Alaska has previously reported infections in a brown bear and a black bear, as well as several red foxes.

It is unclear how the polar bear contracted the virus, but sick birds have been reported in the area. The polar bear could have become infected after eating a dead or sick bird, Dr. Gerlach said.

And scientists don’t know if this case is unique or if there are other infected polar bears that have not been detected. It can be difficult to monitor the virus in wild animal populations, especially those living in places as remote as northern Alaska. “How do you know how many are affected?” Dr. Gerlach said. “We really don’t.”

Local scientists, officials and other experts will continue to look for signs of the virus in wild animals, including polar bears that appear dead or appear sick, Dr. Gerlach said.