#18,846
In a `the plot thickens' moment, this afternoon the Washington State Department of Health has announced their presumptive H5 case announced yesterday has tested positive - not for H5N1 - but for H5N5.
Regular readers know we've been following this relatively rare subtype for several years, mostly seen in Northern Europe, Iceland, and Eastern Canada. Two months ago I wrote:
Another thing we are watching is the slow incursion of HPAI H5N5 - which has been reported in both Canada and Northern Europe (see Svalbard: HPAI H5N5 Detected In Arctic Foxes) - into the United States.
The USDA currently only lists 23 detections (in wild birds) across 4 states (primarily Massachusetts, along with Connecticut, Maine, and Michigan), but given the limits of surveillance and testing, this likely underrepresents its range and impact.
The USDA's most recent update lists 29 (out of 15,709) wild bird samples as H5N5, all reported on the Eastern Seaboard of the United States. That it has turned up on the west coast is noteworthy, and of course, this is the first known human infection with this subtype.
The gist of the emailed announcement from WA DOH follows:
For immediate release: November 14, 2025 (25-138)
Contact: DOH Communications
H5N5 Avian influenza confirmed in Grays Harbor County resident
First detection of this strain in a human, risk to the public remains low
OLYMPIA – A Grays Harbor resident who was hospitalized with influenza symptoms in early November has been confirmed to have influenza A H5, a type of avian influenza. Additional testing shows the virus to be H5N5, an avian influenza virus that has previously been reported in animals but never before in humans. The Centers for Disease Control and Prevention (CDC) and DOH currently considers the risk to the public from avian influenza to be low.
The person is an older adult with underlying health conditions and remains hospitalized. The affected person has a mixed backyard flock of domestic poultry at home that had exposure to wild birds. The domestic poultry or wild birds are the most likely source of virus exposure; however, public health investigation is ongoing. The Washington State Department of Health is working with the local health department and the Washington State Department of Agriculture to complete exposure and animal health investigations.
Public health disease experts have not identified any increased risk to the public.
(Continue . . . )
As of this posting, the WA DOH website has not been updated.
For more on HPAI H5N5, you may wish to revisit:
Svalbard: HPAI H5N5 Detected In Arctic Foxes
Icelandic Food and Veterinary Authority (MAST) : H5N5 Infection In Domestic Cat
Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals
