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.

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?

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.