In Alaska, a fatal case of bird flu has been reported in polar bears

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

“The number of infected mammals continues to rise,” said Dr. Bob Gerlach, Alaska's state veterinarian.

In most cases, the virus has not caused mass die-offs of wild mammal populations. (South American sea lions were one A notable exception.) But it represents a new threat to the already vulnerable polar bear, threatened by climate change and loss of sea ice.

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

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

Fabric samples from the bear last month The test is positive for the virus, according to the Alaska Department of Environmental Protection. The virus was eventually detected in multiple organs, Dr. Gerlach said. “I think it's safe to say he died of a virus,” he said.

Alaska has it Previously reported infections in brown bears and black bears, as well as some red foxes.

It is not known how the polar bear contracted the virus, but sick birds have been reported in the area. The polar bear may have become infected after eating a dead or diseased bird, Dr. Gerlach said.

And scientists don't know if this case is a one-off or if there are other infected polar bears that have escaped detection. It can be difficult to monitor the virus in wild animal populations, especially those living in remote areas like northern Alaska. “How do you know how many are affected?” Dr. Gerlach said. “We certainly don't.”

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