“For example, if a human gets infected with a bird flu and also carries a human influenza A virus, these two viruses can exchange genetic material. This is known as genetic shift,” Michael previously told Fortune. “That can form very new viruses [and] cause epidemics.”

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.