In a development that could deepen concerns over the ongoing H5N1 bird flu outbreak, the U.S. Department of Agriculture (USDA) confirmed the nation’s first case of H5N1 bird flu in a pig. 

This infection occurred on a small farm in Oregon, where poultry and livestock share water and housing—a setup that may have enabled cross-species transmission, officials said. The pig did not show symptoms of illness, but all swine on the farm were euthanized for further testing, with results pending on two of the animals.

This case of H5N1 in swine has sparked renewed attention, given pigs’ reputation as potential “mixing bowl” species for flu viruses. They possess receptors similar to those found in both humans and birds, allowing viruses to potentially mutate within their respiratory systems. Experts note this ability to act as a host for both avian and human viruses could pave the way for more dangerous mutations, recalling the 2009 swine flu pandemic, which is believed to have jumped to humans after mutating in pigs.

Adding to these concerns, health officials recently reported that a second Missouri resident, with no known exposure to infected poultry or dairy cows, tested positive for H5N1. This individual lives with a person who was hospitalized with bird flu in August. Although antibody tests found no evidence of infection among health care workers who treated the original patient, the Centers for Disease Control and Prevention (CDC) emphasized the shared exposure as the likely source of infection, ruling out human-to-human transmission. According to the CDC, while the immediate risk of H5N1 spread remains low for the general public, individuals in close contact with infected animals are at elevated risk.

Since the beginning of the year, bird flu has led to 39 human infections across the United States, primarily linked to infected poultry and cattle. California has reported 16 cases, while Washington state confirmed two infections in poultry workers. Outside Missouri, all confirmed cases have been linked to direct animal exposure.

The continued spread of bird flu has hit the livestock industry hard, with 394 dairy herds across 14 states affected since March. For years, avian influenza has been circulating among wild and domestic birds, but the recent spread to dairy cows, poultry workers, and now pigs underscores the outbreak’s evolution and potential risks.

“We should be very concerned at this point,” cautioned Dr. James Lawler, co-director of the University of Nebraska’s Global Center for Health Security, in an interview with the New York Times. “Nobody should be hitting the panic button yet, but we should really be devoting a lot of resources into figuring out what’s going on.”

As the virus crosses new species barriers, the USDA and CDC continue to monitor the situation closely, maintaining quarantine protocols and investigating transmission pathways to protect animal and human health.