U.S. health officials have confirmed the first case of highly pathogenic avian influenza (H5N1) in a pig in the United States, marking a concerning development in the ongoing bird flu outbreak that has already affected poultry and dairy cattle across the country.
The U.S. Department of Agriculture (USDA) announced on Wednesday that the virus was detected in a pig at a backyard farming operation in Crook County, Oregon. The farm, which houses both poultry and livestock, had already reported H5N1 infections in its poultry on October 25.
"On Tuesday, Oct. 29, the USDA National Veterinary Services Laboratories confirmed one of the farm's five pigs to be infected with H5N1, marking the first detection of H5N1 in swine in the United States," the agency stated in its release.
Cross-Species Transmission Dynamics
The infected pig showed no clinical symptoms of the disease, but was tested due to the confirmed presence of the virus in other animals on the farm. All five pigs at the operation were euthanized for further testing. Results came back negative for two pigs, while results for two others are still pending.
The USDA noted that conditions at the farm likely facilitated transmission between species: "The livestock and poultry on this farm shared water sources, housing and equipment; in other states, this combination has enabled transmission between species."
The farm has been placed under quarantine. Since it is not a commercial operation, the USDA emphasized that "there is no concern about the safety of the nation's pork supply as a result of this finding."
Scientific Concerns About Pigs as "Mixing Vessels"
The detection of H5N1 in swine is particularly concerning to scientists because pigs are considered potential "mixing bowl" species for influenza viruses. They carry receptors on cells in their lungs that are similar to those found in both humans and birds, potentially allowing avian viruses to adapt and become more transmissible to humans.
Dr. James Lawler, co-director of the University of Nebraska's Global Center for Health Security, expressed concern about the development, telling the New York Times, "We should be very concerned at this point. 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."
The 2009 H1N1 swine flu pandemic is believed to have originated from a virus that mutated in pigs in Mexico before jumping to humans, demonstrating the potential public health implications of influenza viruses circulating in swine populations.
Broader H5N1 Situation in the United States
The detection in pigs comes amid a significant and expanding outbreak of H5N1 in the United States. According to the CDC, 39 human cases of bird flu have been reported in the U.S. this year. Most of these cases have been linked to direct exposure to infected poultry or cattle.
Particularly concerning are two recent human cases in Missouri that have no known exposure to infected animals. These individuals, one of whom was hospitalized in August, shared a household. The CDC has indicated that their identical symptom onset dates suggest "a single common exposure to bird flu rather than person-to-person spread within the household."
The outbreak has affected more than 394 dairy herds across 14 states since March, when the virus was first confirmed in dairy cattle. The virus has been spreading in wild and domestic birds in the United States for several years.
State-Level Impacts
The spread of H5N1 is also affecting poultry operations in various states. Georgia, the nation's leading poultry producer, recently confirmed its first case of bird flu in a commercial poultry flock in Elbert County. This marks the fifth detection of HPAI in Georgia but the first in a commercial operation since the current outbreak began in 2022.
Georgia Agriculture Commissioner Tyler Harper emphasized the gravity of the situation: "This is a serious threat to Georgia's number one industry and the livelihoods of thousands of Georgians who make their living in our state's poultry industry."
Public Health Implications
While the CDC maintains that "the immediate risk to the general public from H5N1 bird flu remains low," the agency acknowledges that "people with exposure to infected animals are at higher risk of infection."
The expanding range of affected species and the increasing number of human cases underscore the need for continued vigilance and robust surveillance systems. Public health officials continue to monitor the situation closely, particularly for any evidence of sustained human-to-human transmission, which has not yet been identified in the United States.
As the virus continues to spread across species barriers, researchers and public health officials are intensifying efforts to understand its evolution and develop effective countermeasures to prevent a potential pandemic.
