The first U.S. bird flu death has been reported — a person in Louisiana who had been hospitalized with severe respiratory symptoms.Louisiana health officials announced the death on Monday.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.They have disclosed few other details about the person.Since March, 66 confirmed bird flu infections have been reported in the United States, but previous illnesses have been mild, and most have been detected among farm workers exposed to sick poultry or dairy cows. In two cases — an adult in Missouri and a child in California — health officials haven't determined how they caught it.The origin of the Louisiana person’s infection wasn't considered a mystery. But it was the first human case in the United States linked to exposure to backyard birds, according to the federal Centers for Disease Control and Prevention.Louisiana officials said they aren't aware of any other cases in their state, and U.S. officials have said they do not have any evidence at this point that the virus is spreading from person to person.The H5N1 bird flu has been spreading widely among wild birds, poultry, cows and other animals. Its growing presence in the environment increases the chances that people will be exposed to and possibly catch it, officials have said.Officials continue to urge people who have contact with sick or dead birds to take precautions, including wearing respiratory and eye protection and gloves.