A Washington state resident has been diagnosed with a bird flu strain never before seen in humans, marking an unprecedented case that has alarmed public health officials. The “severely ill” man, who was admitted to hospital with high fever, confusion, and respiratory distress, tested positive for H5N5, a subtype of avian influenza usually found in ducks, geese, and other wild birds.
According to the Washington State Department of Health, H5N5 has only been detected in animals until now. The patient, described as older with underlying medical issues, lives in Grays Harbor County and keeps a mixed backyard flock. Two of his birds had recently died, raising concern that infected poultry or wild birds may have been the source.
Health authorities are now conducting a full investigation alongside agricultural officials to determine how the virus made the jump to a human for the first time. Early evidence suggests the man had close contact with infected or sick birds. Despite the alarming nature of the case, officials stress that the general public is not at increased risk.
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What Exactly Is H5N5?
H5N5 belongs to the 2.3.4.4b clade of highly pathogenic avian influenza (HPAI), a fast-evolving and dangerous lineage that has caused massive outbreaks in animals since 2020. It is considered a newer genetic branch of the well-known H5N1 strain.
Avian influenza viruses, which naturally circulate in wild aquatic birds, can infect domestic poultry and sometimes mammals. Human infections are rare and typically occur after direct exposure to sick or dead birds. According to the Washington Department of Health, reported cases in the U.S. have ranged from mild to severe, with only one fatality historically recorded.
Crucially, human-to-human transmission of avian influenza remains “extremely rare” and has never been documented in the United States.
Officials are continuing to track exposure pathways and monitor close contacts as scientists work to understand how, and why, H5N5 crossed the species barrier for the first time.