H5N1 influenza has now been detected in pigs. This was something virologists had been worrying about ever since this highly pathogenic strain of bird flu started its rapid global spread in 2020. But why were we worrying specifically about pigs? And does this case – detected on a farm in Oregon on October 29 – change anything?

Birds and humans have different types of receptors in their respiratory tract that flu viruses attach to, like a lock (receptors) and key (virus). The attachment of the virus allows it to invade a cell and the body and cause illness. Avian flu viruses are adapted to birds, and spread easily among birds, but not in humans.

The United States Department of Agriculture last week reported that a pig on a backyard farm in Oregon was infected with bird flu.