Researchers say the United States is not on a path to contain the bird flu on dairy farms. (Stephen Ausmus/Animal Research Services, USDA) Keith Poulsen’s jaw dropped when farmers showed him images on their cellphones at the World Dairy Expo in Wisconsin ...

The CDC has confirmed a total of 66 human cases of bird flu across the United States as of Friday, although the number is believed to be higher.

The ongoing spread of bird flu in the United States has alarmed experts -- not just because of human cases causing severe illness, but also due to troubling new instances of infections in cats.

A new bird flu mutation of H5N1 has been discovered in a patient in the US state of Louisiana. Public health officials are concerned the new strain may rapidly develop, increasing its ability to affect humans.

A genetic analysis suggests the bird flu virus mutated inside a Louisiana patient who contracted the first severe case of the illness in the United States

The bird flu virus found in a severely ill patient hospitalized in the United States has mutated to become better adapted to human airways, though there is no evidence it has spread beyond the individual,

Tiny genetic alterations could help the bird flu virus enter cells in the upper respiratory tract, the C.D.C. said. But there is no sign that mutations are widespread in nature.

A patient in Louisiana became severely ill after contracting Highly Pathogenic Avian Influenza (HPAI), the US Centers for Disease Control and Prevention (CDC) announced in a statement on Thursday. This is the first serious case of bird flu affecting a human reported in the US since the outbreak began.