New Strain of Bird Flu Hospitalizes Washington Resident
A resident from Washington has been hospitalized due to a new strain of bird flu, known as H5N5. State health officials shared this information on Friday, stating that this marks the first recorded human infection of the H5N5 bird flu virus.
The individual had a mixed flock of backyard birds that may have come into contact with wild birds, which are likely sources of the infection, according to the Washington State Department of Health. Investigations into the case are ongoing.
This incident is notable as it is the first human case of bird flu in the U.S. since February. The patient, an older adult with pre-existing health conditions, remains in the hospital. Health officials had initially reported a preliminary diagnosis on Thursday, which was confirmed the following day.
While H5N5 is a new variant, experts believe it doesn’t pose a greater threat to human health compared to the H5N1 virus, which led to around 70 reported human cases in the U.S. during 2024 and 2025. Most of those cases were mild and involved workers on dairy and poultry farms.
Richard Webby, a flu researcher at St. Jude Children’s Research Hospital, explained that both H5N5 and H5N1 viruses share similar behaviors. He said, “My gut instinct is to consider it the same as H5N1 from a human health perspective.”
The Centers for Disease Control and Prevention (CDC) also stated there’s no evidence that public health risks have increased due to this new case. They are currently waiting for a sample from Washington to conduct more tests.
The key difference between H5N5 and H5N1 lies in the proteins involved in how the virus spreads, Webby noted. He compared different flu strains to various brands of car tires, suggesting that while they serve the same function, they are better suited to different scenarios.
Bird flu has been affecting various bird populations since early 2022, and it was even detected in dairy cows for the first time last year. The virus can infect not only birds but also mammals like pigs, cattle, and even cats. People can become infected mainly through close contact with infected animals, which is why farm workers are at a higher risk.
