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 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,

The U.S. Centers for Disease Control and Prevention said on Thursday its analysis of samples from the first severe case of bird flu in the country last week showed mutations not seen in samples from an infected backyard flock on the patient's property.

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.

Connecticut has not been spared from the ongoing bird flu outbreak that has primarily been impacting livestock.

Highly contagious H5N1 avian influenza, or “bird flu,” has been found in a Mississippi chicken flock. It’s the first major case of bird flu in Mississippi since 2023.

Exclusive reporting reveals how the United States lost track of a virus that could cause the next pandemic. Problems like the sluggish pace of federal action, a deference to industry, and neglect for the safety of low-wage workers put the country at risk of another health emergency.