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

After someone in southwest Louisiana was hospitalized with a severe case of bird flu, the first such illness reported in the United States, health workers swabbed the person’s nose and throat, looking for genetic clues about the virus.

Growing concerns surrounding the transmission of H5N1 bird flu. The CDC reports that samples collected from a severely ill patient in Louisiana showed signs of mutation, as they differ from the samples collected from sick and dead birds believed to have infected the man in the first place.