H3N1 influenza strains recently seen in U.S. swine could pose risks for people and pigs, according to federal animal health authorities.
The Department of Agriculture said in a joint announcement with the American Association of Swine Veterinarians and National Pork Board that several H3N1 strains had been found in at least two states since December 2013. Such strains are rarely found in U.S. swine, and these occurrences require further examination, the announcement states.
Two of the strains contain a gene associated with human seasonal influenza, distinguishing it from other current H3 influenza viruses circulating in swine.
“Potential spread of H3N1 or H3N2 that carries the human-like H3 could have significant impact in swine herds due to poor herd immunity as well as potential public health ramifications,” the announcement states.
Preliminary findings from the USDA Agricultural Research Service indicate isolates that contain the “human-like H3 gene” are virulent and able to cause disease.
The announcement was sent to pig owners, veterinarians, and members of the National Animal Health Laboratory Network.
A spokeswoman for the Centers for Disease Control and Prevention said in mid-September that the CDC had not received any recent reports of human infections with H3N1.