H5N1 bird flu virus has been found in a pig on a farm in Oregon, the first time the virus has been seen in a pig in the United States, the U.S. Department of Agriculture reported Wednesday.
The pig, one of five on the farm, did not display signs of illness. Two others tested negative and testing is ongoing on the other two. All five were euthanized to allow for study of whether the animals were truly infected.
Pigs are sometimes called a “mixing bowl” for flu viruses, because they can be infected with both bird flu viruses and human flu viruses. If they are coinfected at the same time with two or more viruses, the viruses can swap genes, potentially creating a hybrid virus that is better able to spread to and among people than bird flu viruses typically are. This phenomenon, called reassortment, is what gave rise to the 2009 H1N1 pandemic.
Because pigs can play this role, flu experts have been worried that the H5N1 virus currently spreading in cows in the United States could make its way to pigs. It’s not currently known if the virus found on the Oregon farm is the same version of the virus.
Several influenza experts STAT spoke to Wednesday were waiting for more details before drawing conclusions about the significance of this finding.
“If it doesn’t spread from pigs to pigs and it just happened on that one farm, it’s not a big deal. If it starts to spread from pigs to pigs, then it’s much more of a problem,” said Florian Krammer, a flu virologist at Mount Sinai’s Icahn School of Medicine in New York.
“If it ends up in large big populations in the U.S. similar to cows, I think this would be a disaster.”
In its statement, the USDA said the outbreak was on a backyard farm in Oregon that had poultry and several types of livestock — pigs, sheep, and goats. The farm is not a commercial operation. The entire farm is under a quarantine order and the other animals remain under observation.
This is a breaking story and will be updated.