The H5N1 strain of avian flu has been detected in a pig for the first time in the US, its department of agriculture has confirmed.

The US Department of Agriculture (USDA) said it was identified in a backyard farming operation in Crook County, Oregon, on Tuesday 29 October.

The backyard farm has a mix of poultry and livestock, including pigs.

A couple of days prior, on Friday 25 October, Oregon department of agriculture announced that poultry on this farm represented the first H5N1 detection in Crook County.

The pigs were subsequently tested, with one of the five infected with the H5N1 strain of bird flu.

The other pigs were euthanised to facilitate additional diagnostic analysis. Test results were negative for two of the pigs, and test results are still pending for two others, the USDA said.

“The livestock and poultry on this farm shared water sources, housing and equipment. In other states, this combination has enabled transmission between species.

“Although the swine did not display signs of illness, the Oregon Department of Health and USDA tested the five swine for H5N1 out of an abundance of caution and because of the presence of H5N1 in other animals on the premises,” the USDA added.

No threat to food supply

As this farm is a non-commercial operation, the animals were not intended for commercial food supply.

The USDA said there is no concern about the safety of the nation’s pork supply as a result of this finding.     

The farm has been quarantined to prevent further spread of the virus. Other animals, including sheep and goats on the farm, remain under surveillance.  

Since April 2024, the USDA has confirmed H5N1 in 39 commercial poultry flocks and 28 backyard flocks, totalling over 22m birds affected.

Public health risk low

In respect of this identification, the USDA’s laboratories did not find any changes to the H5N1 virus that would suggest that it is more transmissible to humans, indicating that the current risk to the public remains low.

Since April 2024, the Centre of Disease Control (CDC) has confirmed H5N1 bird flu infections in 36 people in the US. Of these, 16 cases were in California, three of which were confirmed last week.

Fifteen of these cases were associated with exposure to bird flu-infected poultry and 20 were associated with exposure dairy cows infected with the disease.

Since March 2024, when the disease was first detected in dairy cattle the USDA has confirmed infected cattle in 387 dairy herds in 14 states.