The detection of H5N1 avian influenza (bird flu) in a pig on an Oregon farm has again raised concerns specifically among virologists who monitor infectious diseases. Although this might seem insignificant compared to the extensive impact bird flu has had on wildlife and agriculture globally,

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 UK government said on Tuesday that cases of bird flu had been confirmed in commercial poultry at premises in Yorkshire, hours after it increased the risk level of the disease from medium to high.

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

In many ways, the initial reports of this case are – against the backdrop of a continuing viral outbreak that has devastated seabird colonies around the world, caused huge die-offs of sea lions and led to the emergence of an entirely new disease of US dairy cattle – pretty innocuous.