Lead: A Washington state resident was confirmed Friday to be infected with an H5N5 avian influenza virus, the first known human case of that subtype and the first U.S. human bird-flu case since February. The patient, an older adult with underlying health conditions from Grays Harbor County, remains hospitalized. State health authorities announced a preliminary diagnosis on Thursday and confirmed the subtype on Friday. Officials are investigating exposure, noting the person kept a backyard flock that had contact with wild birds.
Key Takeaways
- This is the first confirmed human H5N5 infection in the United States and the first human bird-flu case since February.
- The patient is an older adult from Grays Harbor County with underlying health conditions and is currently hospitalized.
- State officials announced a preliminary positive test Thursday and confirmed H5N5 on Friday after further testing.
- H5N5 differs from H5N1 in a protein that helps release virus from infected cells; that difference may affect bird host preference.
- Public-health agencies, including the CDC, say there is no evidence the case increases risk to the general public.
- In 2024–2025 the H5N1 virus was linked to about 70 reported human infections in the U.S., mostly mild illnesses in farm workers.
- Investigators consider domestic poultry or wild birds the most likely exposure source; additional laboratory testing is pending.
Background
Avian influenza viruses occasionally infect humans, most often after direct contact with infected birds or contaminated environments. The H5N1 lineage produced a wave of roughly 70 reported human infections in the United States across 2024 and 2025, primarily involving workers on dairy and poultry operations and, for the most part, causing mild illness. Public-health surveillance intensified after those events, with state and federal labs routinely testing suspect human and animal samples for subtypes and genetic changes.
H5 subtypes are designated by differences in surface proteins; small molecular variations can alter which bird species a virus favors and, in some cases, how well it replicates in mammals. State agriculture and health agencies monitor poultry flocks, wild-bird gatherings and farm-worker exposures because zoonotic spillover events tend to be the earliest warning of change. Local veterinary reports and laboratory sequencing together guide risk assessments when a human case is identified.
Main Event
On Thursday, Washington state health officials reported a preliminary positive test for avian influenza in an older adult from Grays Harbor County who keeps a backyard flock that had contact with wild birds. By Friday, state laboratories—backed by federal partners—confirmed the virus subtype as H5N5. The patient has been hospitalized and has preexisting medical conditions; officials have not released the patient’s name or detailed clinical status.
Investigators say the backyard poultry and nearby wild birds are the most likely sources of exposure. State and federal teams collected specimens from the person and from local birds; the CDC is expected to perform additional confirmatory testing on specimens forwarded from Washington. Officials emphasized that there is no current indication of sustained human-to-human transmission.
Laboratory analysis highlighted that H5N5 differs from the H5N1 viruses that circulated in recent U.S. human cases by a protein implicated in viral release from infected cells and spread to neighboring cells. That molecular distinction can influence which bird species the virus infects most readily, though how that translates to human risk remains under evaluation.
Analysis & Implications
The immediate public-health message from federal and state agencies is measured: available evidence does not suggest an increased threat to the public compared with recent H5N1 activity. Given the 70 H5N1 human cases in 2024–2025 were largely mild and linked to animal exposure, authorities are focusing on containment at the human-animal interface—testing, quarantine of affected birds, and guidance for people who handle poultry.
However, any zoonotic event requires close genomic surveillance because influenza viruses can acquire mutations or reassort when co-circulating in birds or mammals. A single confirmed human infection is not, by itself, a sign of altered pandemic potential, but it is a data point that could prompt more intensive sequencing and epidemiological tracing around the case and local flocks.
For healthcare systems and local public health, the case underlines the need to maintain testing capacity and clear clinical guidance for clinicians who evaluate patients with bird exposure and respiratory symptoms. It also reinforces workplace protections and monitoring for agricultural workers who are at higher occupational risk from avian viruses. Internationally, the finding will be noted by WHO and other surveillance networks coordinating information about avian influenza subtypes in birds and humans.
Comparison & Data
| Metric | H5N1 (2024–25) | H5N5 (current) |
|---|---|---|
| Reported U.S. human cases | ~70 | 1 |
| Typical clinical severity (reported) | Mostly mild in farm workers | Hospitalized older adult (under investigation) |
| Likely sources | Dairy/poultry operations, wild birds | Backyard poultry/wild birds |
The table places the new H5N5 case in context: epidemiologically it is a single event compared with an earlier cluster of human H5N1 infections. While numbers do not indicate broader spread of H5N5 to humans, investigators will use genomic data and contact tracing to determine whether this represents isolated spillover or something that warrants expanded testing in the region.
Reactions & Quotes
Federal and academic voices offered cautious reassurance while stressing surveillance.
“These viruses behave similarly. My gut instinct is to consider it the same as H5N1 from a human health perspective.”
Richard Webby, St. Jude Children’s Research Hospital (flu researcher)
Webby framed the subtype difference as a likely narrow biological variation that does not, on current evidence, imply a greater human health threat.
“No information would suggest the risk to public health has increased as a result of this case.”
Centers for Disease Control and Prevention (official statement)
The CDC statement echoed state authorities, emphasizing that routine public-health measures remain appropriate while further testing proceeds.
Unconfirmed
- Exact route of transmission remains unconfirmed; investigators suspect backyard poultry or wild birds but confirmation is pending.
- Whether H5N5 has different transmissibility in humans compared with recent H5N1 strains is not yet established.
- The extent of any additional human infections linked to this event has not been reported and remains under active investigation.
Bottom Line
The confirmed H5N5 infection in a Washington resident is a notable zoonotic event but, on available evidence, does not indicate heightened public risk compared with recent H5N1 activity. Public-health agencies are relying on testing, genomic sequencing and epidemiologic tracing to clarify exposure pathways and to detect any secondary spread.
For the public, standard precautions around sick or dead wild birds and backyard poultry remain the practical defense: avoid unprotected contact, follow state guidance on poultry testing and disposal, and seek medical assessment if respiratory symptoms develop after bird exposure. Officials will update guidance if new evidence changes the assessment.
Sources
- Associated Press — initial news report and state official statements (News)
- Centers for Disease Control and Prevention — avian influenza information and statements (Official public-health agency)
- St. Jude Children’s Research Hospital — research and expert commentary (Academic/research)