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Rare H5N5 Bird Flu Infects Washington Resident
15 Nov
Summary
- First known human case of H5N5 bird flu in the U.S.
- Infected person has underlying health conditions and is hospitalized
- H5N5 virus not believed to pose greater threat than previous H5N1 strain
On November 15, 2025, health officials in Washington state confirmed that a resident has been infected with a rare strain of bird flu known as H5N5. This marks the first known human case of the H5N5 virus in the United States.
The infected individual is an older adult with underlying health conditions and is currently hospitalized. State and federal health authorities are investigating the source of the exposure, with the most likely culprits being the person's backyard flock of domestic poultry or contact with wild birds.
While the H5N5 strain is a new variant, health experts do not believe it poses a greater threat to human health compared to the H5N1 bird flu virus that caused a wave of 70 reported infections in the U.S. over the past two years. Most of those previous cases resulted in mild illnesses, primarily among workers on dairy and poultry farms.
"These viruses behave similarly," said Richard Webby, a prominent flu researcher at St. Jude Children's Research Hospital. "My gut instinct is to consider it the same as H5N1 from a human health perspective."
The Centers for Disease Control and Prevention has issued a statement saying the new H5N5 case does not indicate an increased risk to the general public. Additional testing is underway to better understand this novel strain.
