U.S. resident infected with H5N5 — a different type of bird flu

A Washington State resident has bird flu, and it’s a different type than what was seen in previous infections, State health officials said on November 15, 2025.

It is the nation’s first human case of bird flu since February. The older adult with underlying health conditions remains hospitalized.

State health officials had announced the preliminary bird flu diagnosis on November 14. The next day, they said it had been confirmed.

The person was infected with a bird flu called H5N5, state officials said. State and federal health officials said it appears to be the first known human infection with the H5N5 bird flu virus.

That version is not believed to be a greater threat to human health than the H5N1 virus behind a wave of 70 reported human infections in the U.S. in 2024 and 2025. Most of those have been mild illnesses in workers on dairy and poultry farms.

“These viruses behave similarly,” said Richard Webby, a prominent flu researcher at St. Jude Children’s Research Hospital in Memphis, Tennessee. “My gut instinct is to consider it the same as H5N1 from a human health perspective.”

The Centers for Disease Control and Prevention on Friday issued a similar statement that said no information would suggest “the risk to public health has increased as a result of this case.”

The agency is awaiting a specimen from Washington to conduct additional testing.

The distinction between H5N5 and H5N1 lies in a protein involved in releasing the virus from an infected cell and promoting spread to surrounding cells.

“Think along the lines of different brands of car tires. They both do the same job, it’s just each is better tuned for specific conditions, which we don’t fully understand,” Webby wrote in an email.

H5N5 may have a different preference for which kind of birds it most readily infects, he added.

The Grays Harbor County resident, who has not been identified, has a backyard flock of domestic poultry that had been exposed to wild birds, health officials said. They believe the domestic poultry or wild birds are the most likely source of exposure, but say they are still investigating.