In a positive finding, the CDC emphasized that there is no evidence the virus has spread from the Louisiana patient to others, and the mutations alone are unlikely to spread from person to person. CDC scientists also confirmed, however, that the Louisiana virus samples are closely related to candidate vaccine strains already developed for bird flu.

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.

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,

Federal health officials say that not only has a Louisiana resident contracted the first severe case of bird flu in the U.S., but that the virus likely mutated in the patient. The findings raise concern regarding the adaptability of the virus.