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 genetic analysis of the bird flu in the body of a Louisiana man who contracted the first severe case found it mutated inside of his body, a development that could allow the virus to more easily spread to humans.

The genetic analysis of the H5N1 avian flu virus in specimens from the nation's first severely ill hospitalized patient in Louisiana reveals mutations that may enable upper-airway infection and greater transmission, concludes a technical summary from the Centers for Disease Control and Prevention (CDC).