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 reported more than double the cases of norovirus, commonly known as stomach flu, compared to previous years in early December.

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.

Outbreaks of the highly contagious stomach virus are more than double what they were last year at the time, CDC says. Protect yourself by washing hands with soap often — antibacterial gel doesn't work well against the virus.

The latest government data shows that cases of a fast-spreading stomach bug are surging in parts of the United States. The most recent numbers from the U.S.