NEW YORK (AP) — The first U.S. bird flu death has been reported — a person in Louisiana who had been hospitalized with severe respiratory symptoms.

State health officials announced the death on Monday, and the Centers for Disease Control and Prevention confirmed it was the nation’s first due to bird flu.

Health officials have said the person was older than 65, had underlying medical problems and had been in contact with sick and dead birds in a backyard flock. They also said a genetic analysis had suggested the bird flu virus had mutated inside the patient, which could have led to the more severe illness. Few other details about the person have been disclosed.

Since March, 66 confirmed bird flu infections have been reported in the U.S., but previous illnesses have been mild and most have been detected among farmworkers exposed to sick poultry or dairy cows.