SALEM — Oregon wildlife officials said they have diagnosed a handful of wild mammals with highly pathogenic avian flu – but they do not consider it an outbreak.

The disease, commonly known as bird flu, is usually associated with wild birds and backyard flocks. It has killed thousands of birds throughout the state in recent months and led to the death and euthanization of millions of chickens and other domestic birds across the U.S.

The U.S. Agriculture Department has recorded avian flu infections in 110 mammals across the country since May 2022, including six skunks and one raccoon in Oregon. The disease has not affected the state’s wildlife populations, said state wildlife veterinarian Colin Gillin.

In other parts of the U.S., foxes, coyotes, bobcats, fishers, possums, bears and even seals and dolphins also were found to carry the disease.

Health officials say it’s rare for bird flu to spill over to mammals and the risk to humans is very low, though several hundred people across the world have tested positive for the disease in past years.

Typically, the wild mammals diagnosed are scavengers who likely ate a very sick or recently dead bird that carried bird flu, said Gillin. The animals also might have contracted the disease by congregating in areas contaminated with the virus, which can survive in feces or mud for several days.

Transmission of bird flu from mammal to mammal has not been observed so far in Oregon or elsewhere, Gillin said, except on mink farms where the animals are packed in cages nose to nose, with little ventilation. In the wild, he added, most animals don’t congregate in large groups and are usually outside in the open air.

Human infections with bird flu have most often occurred after close or lengthy contact with infected birds or places that the birds touched, according to the Centers for Disease Control and Prevention. While more than 800 cases have been recorded world-wide since 2003, fewer than 10 cases have been reported since 2021. The U.S. recorded its first case of avian influenza in humans last April.

Owners of backyard flocks should be especially cautious about letting their birds go outside if nearby properties have ponds where wild birds could land, Gillin said. They also should watch for wild animals who might be sick or dead, he said.

In one recent case in Columbia County, investigators with the Oregon Department of Agriculture who responded to a backyard flock sick with bird flu found six skunks dead nearby, department spokeswoman Andrea Cantu-Schomus said.

Approximately 20 birds in a noncommercial flock had to be euthanized, she said. The skunks were sent to the Oregon Department of Fish and Wildlife and tested positive for bird flu.

It’s unclear whether the dead skunks had contracted bird flu by eating contaminated backyard birds or wild birds or by being present in an environment contaminated by the virus, Gillin said.

Deadlier strains of bird flu have been on the rise in recent years. Highly pathogenic avian influenza has devastated wild birds and the poultry industry across the globe. The virus is now endemic in Europe and Asia.

And avian flu cases will likely increase soon in Oregon and elsewhere, Gillin said, as wild birds start to migrate from their southern wintering grounds up north as part of their annual migrations. As more wild birds and backyard flocks get sick, more mammals might also be diagnosed.