The first US bird flu death has been reported – a person in Louisiana who had been hospitalised 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 back garden 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 US, but previous illnesses have been mild and most have been detected among farmworkers exposed to sick poultry or dairy cows.
A bird flu death was not unexpected, virus experts said. More than 460 people have died from versions of the H5N1 bird flu virus since 2003, according to the World Health Organization.