Washington resident dies of complications from a bird flu strain never before reported in humans.

### Breaking: First Human Death from Novel H5N5 Bird Flu Strain in Washington State

On November 21, 2025, the Washington State Department of Health (DOH) announced the death of a resident from Grays Harbor County due to complications from an H5N5 avian influenza infection—the first confirmed human case of this strain worldwide. The patient, an older adult with underlying health conditions, was hospitalized in King County in early November after developing flu-like symptoms. Testing at the University of Washington Medicine Clinical Virology Lab, confirmed by the CDC, identified the virus as H5N5, which had previously only been detected in birds and mammals (first reported in eastern Canada in 2023) but never in humans.

#### Key Details of the Case

- **Patient Profile**: The individual maintained a backyard flock of mixed domestic poultry exposed to wild birds, which is the most likely source of infection. Environmental samples from the flock tested positive for avian influenza.

- **Timeline**: Hospitalized in early November 2025; death reported on November 21.

- **Broader Context**: This marks the first U.S. human bird flu case in nine months and the second bird flu-related human death in the U.S. since the 2022 outbreak began (the prior fatality was in Louisiana in early 2025 from an H5N1 variant). Over 70 other U.S. human cases since 2022 have mostly been mild, linked to poultry or dairy workers.

#### Public Health Response and Risk Assessment

Health officials are monitoring over 100 close contacts (including those exposed to the patient and the backyard flock), but no additional infections have been detected, and there's no evidence of human-to-human transmission. The CDC and DOH emphasize that the overall risk to the general public remains **low**, as H5N5 does not appear more transmissible or severe than the ongoing H5N1 strain. However, experts note concerns about potential viral evolution: if co-infected with seasonal flu, the virus could reassort genes, gaining mutations for easier mammal-to-mammal spread.

H5N5 differs from H5N1 in a key protein that aids viral release from cells, but it carries a mutation observed in infected animals that may enhance mammalian transmission.

#### What This Means for Bird Flu Surveillance

Avian influenza A viruses like H5N5 naturally circulate in wild aquatic birds and can spill over to domestic poultry, mammals (e.g., cattle, cats, pigs), and rarely humans. The 2022 U.S. outbreak has seen unprecedented spread to mammals, prompting heightened monitoring. This case underscores zoonotic risks from backyard flocks and wild bird exposure, especially in regions like the Pacific Northwest with migratory bird pathways.

#### Prevention Recommendations

To minimize risk:

- **For Poultry/Animal Handlers**: Wear protective gear (e.g., masks, gloves) when handling birds or cleaning contaminated areas. Report sick/dead birds to the Washington State Department of Agriculture (1-800-606-3056) or online.

- **General Public**: Avoid contact with sick/dead wildlife or poultry. Clean bird feeders thoroughly. Do not consume raw/undercooked poultry, unpasteurized milk, or feed these to pets.

- **Vaccination**: Get the seasonal flu shot—it's crucial for those around birds, as it reduces the odds of dual infection that could drive viral mutations (though it doesn't prevent bird flu directly).

- **Reporting**: Notify the Washington Department of Fish and Wildlife for sick wild birds/animals.

For updates, check the [CDC's avian flu page](https://www.cdc.gov/flu/avianflu/index.htm) or [Washington DOH](https://doh.wa.gov/emergencies/infectious-disease-outbreaks/outbreaks/avian-influenza). This incident highlights the need for vigilant global surveillance, but authorities stress no cause for widespread alarm.