A Washington state resident has made history as the first person in the United States to test positive for a rare bird flu strain never previously detected in humans.
The older adult, who has pre-existing health conditions, required hospitalization in early November following the onset of a high fever, confusion, and respiratory difficulties.
State epidemiologist Dr. Scott Lindquist told The Washington Post: “This is a severely ill patient.”
Experts emphasize that the public health risk continues to remain low.
Joint testing conducted by the Washington State Department of Health and the U.S. Centers for Disease Control and Prevention (CDC) confirmed the patient was infected with H5N5, an avian influenza type observed in wild birds throughout the U.S. and Canada, but never previously identified in a human.
Officials reported that the person maintains a mixed backyard flock, and two birds had perished weeks earlier. Wild birds also had access to the property, suggesting poultry or wild birds as the most probable exposure source.
Although H5N5 differs from the more prevalent H5N1 strain that has circulated extensively among animals and people globally, experts indicate the two strains exhibit similar characteristics.
Richard Webby, a virologist at St. Jude Children’s Research Hospital, told The Post: “The H5N5 viruses we have looked at behave similarly to H5N1 viruses in our models to assess human risk.”
More than 100 health care workers who had contact with the patient have undergone monitoring, and some received testing for flu-like symptoms.
State health officer Dr. Tao Kwan-Gett said to The Post: “We have identified no additional individuals other than the patient who is infected with H5N5.”
The CDC is collaborating closely with Washington state and has been assisting clinicians with treatment recommendations.
Currently, officials report no evidence of person-to-person transmission.
According to the CDC, cases in U.S. poultry flocks started increasing in September, with 25 flocks infected during the first two weeks of November, already exceeding all of September’s total.
Seema Lakdawala, a virologist at Emory University, explained to The Post that risk escalates during colder months because migratory birds can transport the virus and transmit it to backyard flocks or commercial poultry.
The CDC also maintains vigilance for a potential early increase in seasonal flu, which has already begun rising in some countries.
Since 2024, 70 people in the U.S. have tested positive for bird flu, predominantly workers who had exposure to infected dairy cattle or poultry.