By Leah Douglas and Tom Polansek
CHICAGO (Reuters) – H5N1 bird flu was confirmed in a pig at a backyard farm in Oregon, the first detection of the virus in pigs in the country, the U.S. Department of Agriculture said on Wednesday.
Pigs are of particular concern for the spread of bird flu because they can become simultaneously infected with bird and human viruses, which could swap genes to form a new, more dangerous virus that can more easily infect humans.
The USDA said there is no risk to the nation’s pork supply from the Oregon case and that the risk to the public from bird flu remains low.
Pigs were the source of the 2009-2010 H1N1 flu pandemic and are believed to be the source of others, said Richard Webby, a virologist at St. Jude Children’s Research Hospital who studies flu in animals and birds for the World Health Organization.
The discovery of the virus on a small farm makes the pig infection less concerning than if it had been detected on a commercial pig farm, he said.
“I think it probably doesn’t increase the risk much, but if this virus starts to spread in pigs, it certainly increases the risk,” he said.
The Oregon farm has been quarantined and other animals there, including sheep and goats, are under surveillance, the USDA said.
Pigs and poultry on the farm were culled to prevent the spread of the virus and allow for additional testing of the pigs, the USDA said. Tests are still pending for two of the pigs, the agency said.
The pig case came from wild birds and not from a poultry or dairy farm, a USDA spokesperson said. The migration of wild birds has spread bird flu to poultry flocks and cattle herds.
The case was one of several factors that prompted the USDA to expand its bird flu surveillance to include nationwide testing of bulk milk, which the agency announced on Wednesday, Agriculture Secretary Tom Vilsack told Reuters in an interview.
“While it is a different variant of the virus and linked to wild birds, it is a factor in ensuring we understand and appreciate exactly where the virus is in dairy and cattle,” he said.
The pigs on the Oregon farm were not intended for the commercial food supply, the USDA said.
Still, the finding put pressure on lean hog futures prices on the Chicago Mercantile Exchange, a trader said.
Poultry and pigs on the backyard farm shared water sources, housing and equipment, all of which have served as routes for transmission of the virus between animals in other states, the agency said.
The detection is a warning for pig farmers to be on the lookout for further infections, said Marie Culhane, a professor of veterinary population medicine at the University of Minnesota, who has researched influenza viruses in pigs.
“People need to expand their plans to deal with it if it were to happen in another herd and another herd,” Culhane said. “Pigs are simply very good at picking up flu viruses.”
This year, 36 people have tested positive for bird flu as the virus has spread to almost 400 dairy farms. All but one of the people were farm workers who had had contact with infected animals.
Since 2022, the virus has wiped out more than 100 million poultry birds in the country’s worst-ever bird flu outbreak.
