First Human Case of Influenza A (H5N5) Virus Infection Confirmed in Washington State

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Situation Summary

A Washington resident hospitalized in early November was confirmed to have influenza A (H5N5) virus infection on Nov. 13 and died on Nov. 21, 2025. This is the first known case of influenza A (H5N5) infection in humans.

Testing by Washington State Department of Health detected avian influenza virus in the patient’s backyard flock environment, indicating likely exposure from their backyard flock of mixed domestic birds, their environment, or wild birds. 

The risk of highly pathogenic avian influenza (HPAI) infection for the general public remains low. However, HPAI viruses in wild birds have resulted in outbreaks among commercial poultry and backyard flocks and spread to infect wild terrestrial and marine mammals as well as domesticated animals. Therefore, people with work or recreational exposures to HPAI infected animals are at increased risk of infection. Clinicians should consider the possibility of HPAI in persons showing compatible signs and symptoms with relevant exposure history.

For details on assessment, testing, and management of influenza A (H5), see the Provider Alert from Washington State Department of Health (Nov. 18, 2025).

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Key Points

• Obtain animal exposure history for all patients with suspected or confirmed influenza. Consider adding screening questions to the electronic medical record (EMR). 

  • Assess all patients with suspected or confirmed influenza for exposure to: 

    • Sick or dead animals (wild or domestic), or environments where dead animals have been found.

    • Wild, captive, and livestock animals, including poultry and cattle.

    • Consumption or handling of raw animal products (raw cow milk and products made with raw cow milk, and raw meat-based pet foods).

    • Recent close contact (within six feet) with a symptomatic person suspected or confirmed to have avian influenza. 
      

• Test all hospitalized patients with compatible influenza symptoms and exposure history within 24 hours of presentation.

  • A negative influenza test does not rule out avian influenza. 

  • Collect lower respiratory tract specimens from patients with severe respiratory disease, if possible, in addition to NP, OP, or conjunctival swabs for influenza testing. Lower respiratory tract specimens have a higher yield for detecting HPAI (e.g. HPAI A(H5N1) and A(H7N9).
    

• Consider submitting positive influenza A specimens for subtyping at your facility’s clinical or commercial laboratory. If subtyping is not available through your facility, specimens should be submitted to the Washington State Public Health Laboratories for subtyping.
  

• Immediately report the following to Kitsap Public Health at 360-728-2235: 

  • All suspected and confirmed cases of novel influenza, including H3 and H5, regardless of influenza test results.

  • All influenza A specimens that result as “unsubtypeable” (usually meaning the test result does not detect seasonal influenza).

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Resources

• Signs and Symptoms of Bird Flu in People | Bird Flu | CDC

• Influenza Virus Testing at Washington Public Health Laboratories

• Interim Guidance on the Use of Antiviral Medications for Treatment of Human Infections with Novel Influenza A Viruses Associated with Severe Human Disease | Bird Flu | CDC

• Provider Alert: Case of H5N5 Influenza Confirmed in Washington

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Contacting the Health District

• Call: 360-728-2235 and leave a message. Includes reporting notifiable conditions 24 hours a day, 7 days a week. Leave the patient’s name, date of birth, and disease.

• Fax: 360-813-1168