The Washington State Department of Health (DOH) has confirmed the first human case of the rare H5N5 avian influenza strain in the United States. A resident of Grays Harbor County is hospitalized with the infection, which has not been previously documented in humans. The patient, described as an older adult with underlying health conditions, developed influenza-like symptoms in early November.
This case marks the first known human infection with the H5N5 virus in the country since February. Public health officials have not identified any significant public risk at this time, though the investigation into the source of the infection is ongoing. The DOH stated that the individual had a mixed backyard flock of domestic poultry at home that had exposure to wild birds. Additional testing showed the virus to be H5N5, an avian influenza virus that has previously been reported in animals but never before in humans.
Health experts emphasize that the virus is most commonly spread through domestic poultry and wild birds. However, the exact source of the infection remains under investigation. Officials have not found any increased risk to the public at this time. The Centers for Disease Control and Prevention and DOH both stated that the risk to the public from avian influenza is currently low.
In the wake of this confirmation, the DOH has issued new guidelines, urging poultry owners, wildlife handlers, and others who have contact with animals to take additional precautions. These include avoiding contact with sick or dead birds, using appropriate protective equipment, and reporting sick wildlife or domestic animals to the Washington State Department of Agriculture (WSDA). The release also emphasized that the seasonal flu vaccine does not prevent bird flu infections but is still important because infection with both viruses could lead to the emergence of a more transmissible avian influenza virus.
Previously in 2024, the CDC declared the bird flu emergency officially over, citing declining animal infections and an absence of human cases since February. The H5N5 virus, a close cousin of the H5N1 strain, comes from birds and shares part of its genetic code with the H5N1 strain. However, its different ‘end piece’ of its structure may affect its behavior, according to health officials. While H5N1 has caused human illness and even deaths, H5N5 has largely been limited to birds previously.