When it comes to the potential of H5N1 avian flu, otherwise known as bird flu, picking up mutations that may lead to human-to-human spread, that "train has already left the station," warns one infectious disease expert.

A second type of the virus, D1.1, has been detected in dairy cattle in Nevada, US. A second type of bird flu H5N1 detected in US cattle Some experts believe the risk for humans is low Infections have been detected outside the US,

According to the Centers for Disease Control and Prevention (CDC), there have been 67 confirmed human cases of H5N1 bird flu in the US since 2024. In 64 of those cases, infection has been linked to animal exposure, primarily through dairy cattle herds and poultry farms.

The detection indicates that distinct forms of the virus known as Type A H5N1 have spilled over from wild birds into cattle at least twice. Experts said it raises new questions about wider spread and the difficulty of controlling infections in animals and the people who work closely with them.

State officials say the highly pathogenic avian influenza – more commonly known as bird flu – is widespread in much of the state.