A Washington state resident has been hospitalized with H5N5 bird flu, marking the first time this viral strain has infected a human and raising serious concerns about its unpredictable evolution.

Unprecedented Viral Strain Emerges

Washington State Department of Health officials confirmed Friday that an older adult with underlying health conditions was hospitalized in early November with H5N5 bird flu.

Lab tests revealed that this strain had never before infected humans, distinguishing it from the 71 documented cases since January 2022 involving the H5N1 strain. The patient suffered severe symptoms, including high fever, confusion, and breathing difficulties, before requiring transfer from Grays Harbor County to a King County hospital for specialized care.

Dr. Angela Rasmussen, a Canadian virologist, expressed alarm on social media, stating the viral reassortment represents an “unpredictable” development that could hospitalize someone. This case marks the first bird flu infection detected anywhere in the United States in at least eight months, highlighting the virus’s concerning ability to mutate and cross species barriers. The emergence of H5N5 in humans demonstrates the pathogen’s evolutionary capacity, even as health officials stress that current evidence shows no increased severity compared to other strains.

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Patient Exposure and Contact Tracing

The infected individual owned a mixed backyard flock of domestic poultry and had contact with wild birds prior to falling ill. Two birds in their flock died from an unidentified illness weeks before the human infection, though the remaining birds appear healthy. Officials have not disclosed the patient’s name, gender, specific age, or current treatment status, maintaining medical privacy while conducting epidemiological investigations.

Washington health authorities have traced and tested individuals who had contact with the patient, focusing on those displaying symptoms. As of Friday, no additional bird flu cases were detected among contacts, suggesting limited immediate transmission risk. Bird flu typically spreads through exposure to infected bird saliva or droppings, or through handling deceased infected birds, making direct contact with sick poultry the most likely route of infection for this patient.

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National Outbreak Context

Since the current bird flu outbreak began in January 2022, the virus has devastated American agriculture and wildlife. An estimated 174 million wild and domestic birds have been affected nationwide, with more than 1,000 dairy herds also infected. California leads human infections with 39 confirmed or probable cases, followed by Washington with 15 cases, while one Louisiana resident died from the virus earlier this year.

The timing raises additional concerns, as the wild bird migration season increases the potential for viral spread into new geographic areas. Since September 2024, bird flu has killed 7 million farmed birds nationwide, including 1.3 million turkeys, potentially creating Thanksgiving shortages. Experts warn that the virus’s ability to learn human-to-human transmission could trigger a pandemic similar to COVID-19, though the CDC maintains that the current public health risk remains low while actively monitoring the situation.