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.

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.

Amid a "concerning" new mutation in bird flu that may indicate the virus could begin to more easily infect humans, what are the symptoms to watch for and how worried should you be?

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.

HPAI is considered low risk to humans, the agency said, and there have been no human cases in New England during the current outbreak.

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.