NEW YORK — The U.S. Department of Agriculture reported on Wednesday that a pig on an Oregon farm has been found to have bird flu. This is the first detection of the virus in U.S. swine, raising concerns about its potential to become a threat to humans.

The infection occurred at a backyard farm in Crook County, where animals share water and housing. Poultry at the farm were found to have the virus last week, and testing this week revealed that one of the farm’s five pigs had contracted the infection.

The farm was placed under quarantine and all five pigs were euthanized for further testing. It is not a commercial farm, and U.S. agriculture officials have stated there is no concern about the safety of the nation’s pork supply.

However, the discovery of bird flu in a pig raises concerns that the virus may be gaining a foothold towards becoming a more significant threat to people, according to Jennifer Nuzzo, a pandemic researcher at Brown University.

Pigs can be infected with various types of flu, and they can play a role in adapting bird viruses to better infect humans, she explained. The 2009 H1N1 flu pandemic originated in swine, Nuzzo noted.

“If we’re trying to stay ahead of this virus and prevent it from becoming a threat to the broader public, knowing if it’s in pigs is crucial,” Nuzzo said.

The USDA has conducted genetic testing on the farm’s poultry and has not detected any mutations indicating the virus is developing an increased ability to spread to people. This suggests the current risk to the public remains low, officials said.

Previously, a different strain of the bird flu virus was reported in pigs outside the U.S., but it did not lead to a human pandemic.

“It isn’t a one-to-one relationship, where pigs get infected with viruses and they make pandemics,” said Troy Sutton, a Penn State researcher who studies flu viruses in animals.

This version of bird flu—known as Type A H5N1—has been spreading widely in the U.S. among wild birds, poultry, cows, and various other animals. The persistence of this virus increases the likelihood of human exposure and potential infection, officials say.

Experts believe that the pig infection is not entirely surprising, given the prevalence of the virus in other animals.

The Oregon pig infection “is noteworthy, but does it change the calculation of the threat level? No it doesn’t,” Sutton said. If the virus starts spreading more widely among pigs and if there are ensuing human infections, “then we’re going to be more concerned.”

So far this year, nearly 40 human cases —in California, Colorado, Washington, Michigan, Texas, and Missouri—with mostly mild symptoms, including eye redness, reported. All but one of the people had been to contact with infected animals.