A Washington State resident became the first person ever to die from H5N5 bird flu, marking a chilling milestone as a previously unknown strain crosses into human territory.
Story Highlights
- First human death from H5N5 bird flu strain recorded in Washington State involving older adult with underlying conditions
- H5N5 had never infected humans before this case, representing emergence of new pathogen from animal populations
- Patient contracted virus from backyard poultry flock exposed to wild birds, not commercial agriculture setting
- Experts emphasize H5N5 shows no evidence of greater pandemic risk than dominant H5N1 strain
- Second H5 bird flu death in United States following Louisiana H5N1 fatality in January 2025
Novel Strain Claims First Human Victim
The Washington State Department of Health announced Friday that an older adult with underlying health conditions died from H5N5 avian influenza after being hospitalized since early November. This death represents an epidemiological first—H5N5 had circulated in animal populations but never crossed species barriers to infect humans until now.
The patient maintained a mixed backyard flock of domestic poultry with exposure to wild birds, creating the interface where this viral spillover occurred. Washington State has experienced dozens of H5 detections in wild birds and backyard poultry in recent weeks, establishing the environmental conditions that enabled this transmission.
Watch;
Distinguishing H5N5 From Its Deadlier Cousin
While H5N5 and the more familiar H5N1 share the same hemagglutinin protein, they differ in their neuraminidase components, making them distinct viral subtypes. Richard Webby from St. Jude Children’s Research Hospital emphasized that H5N5 shows no evidence of increased pandemic risk or greater disease severity compared to H5N1.
H5N1 remains the dominant concern due to its widespread presence in bird populations across North America since arriving in late 2021. The mathematical reality means most human exposures will continue involving H5N1 rather than the newly emergent H5N5, though both now require surveillance attention.
Backyard Flocks Create Dangerous Interfaces
This case differs significantly from the 70 previous H5N1 infections in the United States, which primarily occurred among commercial dairy and poultry workers. The Washington victim’s backyard flock represents a growing exposure pathway as H5 viruses establish themselves in wild bird populations nationwide.
Backyard poultry operations often lack the biosecurity measures of commercial facilities, creating direct interfaces between domestic animals and infected wild birds. No other people connected to this case have tested positive, and investigators found no evidence of human-to-human transmission.
Second Death Establishes Troubling Pattern
The Washington death follows the January 2025 Louisiana H5N1 fatality, establishing a pattern of severe outcomes among older adults with underlying conditions. Both victims developed severe respiratory symptoms and required hospitalization before succumbing to their infections.
The CDC now reports 71 total confirmed H5 cases with 2 deaths since tracking began in 2024. While the case fatality rate appears concerning, the small sample size and concentration among vulnerable populations suggests age and comorbidities significantly influence outcomes. Public health officials maintain that risk to the general population remains low despite these tragic losses.
Sources:
University of Nebraska Medical Center – First Human Dies of Rare H5N5 Bird Flu Strain
ABC News – 1st Human Infected with H5N5 Strain of Bird Flu Dies
CIDRAP – First Ever Human Case of H5N5 Avian Flu Confirmed in Washington State
CDC – Bird Flu Situation Summary
