• Posted October 31, 2024

Bird Flu Infection Confirmed in a Pig for First Time in U.S.

Amid an ongoing outbreak of bird flu in poultry and dairy cows in the United States, a case of H5N1 has now been confirmed for the first time in a pig.

"The U.S. Department of Agriculture [USDA] and Oregon state veterinary officials are investigating positive cases of H5N1 in a backyard farming operation in Oregon that has a mix of poultry and livestock, including swine," the USDA said Wednesday in a news release announcing the case.

"The Oregon Department of Agriculture announced on Friday, Oct. 25, that poultry on this farm represented the first H5N1 detection in Crook County, Oregon," the agency added. "On Tuesday, Oct. 29, the USDA National Veterinary Services Laboratories also 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."   

Although the pig did not show symptoms of infection, all five swine on the farm were tested for H5N1 because of the presence of the virus in other animals on the farm. All five pigs were euthanized for further testing, according to the USDA. Results were negative for two of the pigs, while results are pending for two others.   

“The livestock and poultry on this farm shared water sources, housing and equipment; in other states, this combination has enabled transmission between species,” the USDA noted.

The farm has been quarantined, but since it wasn't a commercial farm, “there is no concern about the safety of the nation’s pork supply as a result of this finding,” the agency added.

Scientists have been worried that H5N1 might spread to pigs, which are considered a “mixing bowl” species for flu viruses because they carry the same kind of receptors on cells in their lungs as humans and birds.

In fact, the 2009 swine flu pandemic is believed to have been sparked by a virus that mutated in pigs in Mexico before it jumped to people.

Health officials also reported recently that a second person in Missouri who wasn't exposed to either poultry or dairy cows has been infected with bird flu.

This person shared a home with a patient who was first hospitalized with bird flu in August, but antibody tests have since shown that symptomatic health care workers who cared for the patient were not infected with the H5N1 virus, the U.S. Centers for Disease Control and Prevention said in a bird flu update.

However, there was some reassuring news from Missouri: No evidence that H5N1 had passed person-to-person.

Regarding the household contact of the original hospital patient, the investigation has shown that the fact "that these two individuals had identical symptom onset dates support a single common exposure to bird flu rather than person-to-person spread within the household," the CDC noted.

"To date, human-to-human spread of H5 bird flu has not been identified in the United States," the agency added. "CDC believes the immediate risk to the general public from H5N1 bird flu remains low, but people with exposure to infected animals are at higher risk of infection."

Indeed, the number of human cases of bird flu connected to livestock is rising rapidly in the United States. California has confirmed 16 human cases of bird flu, while Washington state has reported two poultry workers who are infected and five others presumed to be positive.

In total, 39 people have been infected with bird flu in the United States this year, CDC data shows.

Except for the two people in Missouri, all infections so far have been linked to exposure to infected poultry or cattle.

Investigators do not know how the Missouri patient and the household member became infected. They had no exposure to infected animals and had not consumed raw milk products that may have carried the virus, officials said.

The latest cases fuel growing concern among public health experts that the ongoing bird flu outbreak will eventually trigger human-to-human transmission of the virus.

Across the country, more than 394 dairy herds in 14 states have been infected since the outbreak in dairy cows was first confirmed in March. Avian influenza has been spreading in wild and domestic birds in the United States for several years.

“We should be very concerned at this point,” Dr. James Lawler, co-director of the University of Nebraska’s Global Center for Health Security, told 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.”

More information

The CDC has more on bird flu.

SOURCES: Washington State Department of Health, news release, Oct. 24, 2024; U.S. Centers for Disease Control and Prevention, news releases, Oct. 30, 2024; Oct. 24, 2024, Oct. 18, 2024; Oct. 3, 2024; California Department of Public Health, news release, Oct. 23, 2024; New York Times