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.

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.

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.