USDA Confirms Bird Flu in Pig for the First Time

On Oct. 29, the U.S. Department of Agriculture (USDA) National Veterinary Services Laboratories (NVSL) confirmed that one of a backyard farming operation’s five pigs was infected with bird flu, marking the first detection of bird flu in swine in the United States. Earlier last week, the Oregon Department of Agriculture confirmed that poultry on this farm represented the first bird flu detection in Crook County, Oregon.

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 bird flu out of an abundance of caution and because of the presence of bird flu in other animals on the premises. The swine were euthanized to facilitate additional diagnostic analysis.  In addition, the farm has been quarantined to prevent further spread of the virus. Other animals on the farm, including sheep and goats, remain under surveillance.   

USDA’s NVSL also conducted genomic sequencing of viruses from the poultry infected on the farm. That sequencing has not identified any changes to the bird flu virus that would suggest to USDA and the U.S Centers for Disease Control (CDC) that the virus is more transmissible to humans, indicating that the current risk to the public remains low. Additionally, no concern about the safety of the nation’s pork supply arose due to these findings.

As of Nov. 4, the CDC has confirmed 44 total human cases of bird flu infections in six states this year. Nineteen of these cases were associated with exposure to bird flu-infected poultry and 24 were associated with exposure to sick or infected dairy cows. The source of the exposure in one case, which was reported by Missouri on Sept. 6, could not be determined.

The 44 cases include 20 cases in dairy farm workers in California, three of which were confirmed by CDC last week and three on Nov. 4; nine cases in poultry farm workers in Washington state, three of which were confirmed by CDC last week; and one case associated with the Washington poultry outbreak that was confirmed by CDC last week. Cases in California and Washington have occurred in workers on affected farms. 

All available data so far suggest sporadic instances of animal-to-human spread. The farm workers in California and Washington state all described mild symptoms, many with eye redness or discharge (conjunctivitis). Some workers who tested positive in Washington reported some mild upper respiratory symptoms. None of the workers were hospitalized.