A Washington state resident who was undergoing treatment for H5N5 avian influenza died on Friday, the Washington State Department of Health reported.
The person was an older adult with underlying health conditions and had been hospitalized in King County since early November, the health department reported.
The department did not release the patient's name, gender, or age.
Testing at the UW Medicine Clinical Virology Lab identified the virus as H5N5, making this the first recorded infection with this variant in a person globally. The result was confirmed by the Centers for Disease Control and Prevention (CDC), the health authorities said in a press release.
The Washington state resident was infected with a strain that was previously reported in animals but never before in humans, the Washington Post reported. State epidemiologist Scott Lindquist said last week that the person, who was hospitalized after developing high fever, confusion and respiratory distress, was “a severely ill patient," the Post reported.
Health authorities said the risk to the public remains low. No other people involved have tested positive for avian influenza.
Public health officials said they will continue to monitor anyone who was in close contact with the patient for symptoms to ensure that human-to-human spread has not occurred. There is no evidence of transmission of this virus between people.
The individual who died from H5N5 avian influenza had a backyard flock of mixed domestic birds. DOH testing identified avian influenza virus in the environment of the flock, making exposure to the domestic poultry, their environment, or wild birds the most likely source of exposure for this patient. People who had exposure to the backyard flock and environment are also being monitored for symptoms.
In January, a Louisiana patient died from bird flu, the first human case of highly pathogenic avian influenza, or H5N1, in Louisiana and the U.S. It marked the first human death related to bird flu in the U.S.
Since 2024, there have been 71 cases of bird flu in the U.S., according to the CDC. H5 bird flu is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows with sporadic human cases in U.S. dairy and poultry workers, the CDC said.
Avian influenza is a disease caused by influenza type A viruses, which naturally occur in wild aquatic birds around the world. These viruses can infect other bird species, and occasionally mammals, and can be deadly to domestic birds such as chickens and turkeys. On rare occasions, avian influenza viruses can infect people and make them sick, according to the Washington State Department of Health.
"It is especially important that people who may have exposure to domestic or wild birds get a seasonal flu vaccine. While the seasonal flu vaccine will not prevent bird flu infection, it reduces the risk of becoming sick with both human and avian influenza viruses at the same time," public health officials said. "Though unlikely, infection with both viruses could result in the emergence of an avian influenza virus that is more easily transmitted from person to person. Seasonal flu vaccine is recommended for everyone six months and older."