A virologist explains that why this probably isn’t the big one — but that it’s a sign of bad things happening with the virus.

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.

As of December 30, the CDC has confirmed 66 human cases of the bird flu virus in the United States. Most of them were mild infections among dairy workers and others who had contact with infected animals.

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.