Genetic analysis of H5N1 bird flu viruses from a severely ill patient in Louisiana revealed multiple mutations that may enhance the virus’s ability to bind to human upper airway cells, the Centers for Disease Control and Prevention (CDC) reported on Thursday.

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 U.S.

The United States has confirmed its first known severe human infection of H5N1 bird flu, in a person in Louisiana believed to have contracted the virus through contact with sick or dead birds in a backyard flock.