Health Alert: Case of H5N5 Influenza Confirmed in Washington
Nov. 26, 2025

This is a Provider Alert from the Washington State Department of Health (WA DOH) and Snohomish County Health Department regarding a confirmed case of H5N5 influenza in a Washington resident.  

Current Situation: 

 On Nov. 13, 2025, a Washington resident who was hospitalized with respiratory illness symptoms since early November tested positive for influenza A H5, a type of avian influenza. Subsequent sequencing confirmed the patient was infected with H5N5 influenza virus. To our knowledge, this is the first known human case of H5N5. The patient, an older adult with underlying health conditions, died from complications related to this infection on Nov. 21, 2025. 

The patient had a mixed backyard flock of domestic poultry at home; in addition, the flock had exposure to wild birds. The backyard flock or wild birds are the most likely source of the patient's exposure to H5N5. WA DOH is working with the local health department and the Washington State Department of Agriculture to complete public health investigations. 

The Centers for Disease Control and Prevention (CDC) and WA DOH currently consider the risk from highly pathogenic avian influenza (HPAI) to be low for the general public. As seasonal influenza activity begins to increase in Washington and across the United States, the greatest risk to the general public is seasonal influenza, and the best protection remains seasonal influenza vaccination.  

Actions Requested: 

IDENTIFY 

• Be alert for patients with symptoms of influenza.  
  1. Symptoms of avian influenza infection in humans can range from mild to severe. 
  2. Symptoms of avian influenza infection in humans can be similar to symptoms from seasonal influenza viruses; getting an accurate exposure history from symptomatic patients is very important to rapidly identify potential patients with HPAI.  
• Assess exposure history for all patients with suspected or confirmed influenza.  
  1. Assess these patients for the following exposures:  
     • Wild, captive, and livestock animals, including poultry and cattle  
     • Any sick or dead animals or their environment, including pets (i.e., cats, dogs, birds) 
     • Consuming or handling raw animal products (e.g., raw cow milk, products made with raw cow milk, and raw meat-based pet food).  
     • OR recent close contact (within six feet) with a symptomatic person who is suspected or confirmed to have avian influenza. 
  2. If possible, WA DOH recommends adding the above screening questions to the electronic medical record (EMR). 
  3. NOTE: A negative influenza test result does not rule out avian influenza in symptomatic patients with one or more exposures to sources of HPAI. 
  4. Clinicians who suspect HPAI in a patient should immediately notify the patient's Local Health Jurisdiction (see "Notify," below). 
     1. HPAI should remain on the differential with maintenance of contact, droplet and airborne isolation. 

 NOTIFY 

• Clinicians and facilities in all healthcare settings are required to IMMEDIATELY report the following to their Local Health Jurisdiction or Tribal Health Jurisdiction:  
  1. All influenza A specimens that result as "unsubtypeable" (when the subtype of influenza cannot be determined by available tests).
  2. All suspected or confirmed cases of novel influenza, including HPAI (H3 or H5), and regardless of influenza test results.  

TEST 

• Collect specimens for influenza testing as soon as possible after illness onset, ideally within 7 days of first symptoms. Acceptable specimens include: 
  1. nasopharyngeal (NP) swab, or 
• a nasal swab combined with an oropharyngeal (OP) swab (e.g., two swabs collected separately and combined into one viral transport media vial). 
  1. If the patient has conjunctivitis: conjunctival swab. 
• If the patient is severely ill: lower respiratory tract specimens (e.g., an endotracheal aspirate or bronchoalveolar lavage (BAL) fluid from intubated patients, or induced sputum). 
• Test all hospitalized patients with compatible influenza symptoms AND exposure history (when HPAI is suspected) within 24 hours of presentation to the hospital.  
• A negative influenza result does not rule out avian influenza; HPAI should remain on the differential for hospitalized patients with a compatible exposure. 
  • Repeat influenza testing on at least two consecutive days for hospitalized patients. 
• If the patient has severe respiratory disease, consider collecting lower respiratory tract specimens; these specimens have a higher likelihood of detecting avian influenza virus.  
• Positive influenza A specimens should be subtyped if HPAI is suspected (tested to determine the subtype of influenza A, i.e., H1, H3, etc.) 
• Specimens should be submitted for subtyping to your facility's clinical or commercial laboratory, if possible.  
  1. If subtyping is not available, specimens should be submitted to the WA DOH Public Health Laboratories (WAPHL) for subtyping. 
• Follow specimen submission guidelines for all specimens submitted to WAPHL.  

MANAGE 

• Isolate patients with suspected or confirmed HPAI: 
  1. Use contact, droplet, and airborne precautions with eye protection (goggles or face shield). 
• If possible, isolate the patient in an airborne infection isolation room (AIIR; negative pressure). 
• Treat suspect HPAI patients immediately with oseltamivir, do not wait for influenza confirmation.  
• Consider combination antiviral treatment (e.g., oseltamivir and baloxavir) for hospitalized patients with suspected or confirmed HPAI virus infection. 
  1. Refer to CDC's Interim Guidance on the Use of Antiviral Medications  for additional information about treating patients with suspected or confirmed HPAI. 

 ADVISE 

• Advise patients not to handle sick or dead birds or other wildlife.Instead:   
  1. People can report sick or dead wild birds or other wild animals to the Washington State Department of Fish & Wildlife.   
• People can report sick or dead domestic animals, including backyard flocks or livestock suspected of having avian influenza to the Washington State Department of Agriculture. 
• WA DOH and the CDC continue to recommend seasonal influenza vaccine for patients 6 months of age and older.  
• Getting a yearly flu vaccination is the best way to reduce the risk from influenza and its potentially serious complications. 
  1. The 2025-26 seasonal influenza vaccine is a trivalent vaccine covering influenza A(H1N1) virus, an A(H3N2) virus, and a B/Victoria lineage virus.  
• While the seasonal influenza vaccine will not protect against avian influenza, it may prevent patients from getting infected with both strains of influenza at the same time.

Background: 

Avian influenza is a disease caused by influenza type A viruses, which naturally occur in wild aquatic birds around the world. On rare occasions, avian influenza can infect people and make them sick. Most cases have occurred among people who have been exposed to sick or infected animals. The risk of avian influenza increases in the fall and winter because migratory birds can carry the virus and spread it to domestic animals including commercial poultry farms and backyard flocks.  

Transmission of avian influenza between humans is extremely rare and has not been documented in the United States. To ensure that human-to-human spread is not occurring, public health officials are contacting anyone who has been in close contact with the patient to monitor for symptoms and provide testing and treatment as needed.  

CDC has routinely recommended influenza testing for hospitalized patients with suspected influenza. In light of the continued circulation of avian influenza A(H5) virus among wild and domestic animals in Washington state, CDC and WA DOH recommend subtyping of all influenza A virus-positive specimens from hospitalized patients

When possible, especially if there is a compatible exposure history. Recommendation on subtyping my change as the season develops. 

The CDC considers the risk of HPAI A(H5) infections to be low for the general public but is closely monitoring this situation. As seasonal influenza activity begins to increase in Washington and across the United States, the greatest risk to the general public is seasonal influenza. WA DOH publishes a Weekly Influenza Update for seasonal influenza on our Influenza Surveillance Data webpage.  

Resources: 

 For more information about H5 Influenza, please visit: 

• WA DOH: Avian Influenza  
• WA DOH: Influenza Surveillance Data (Weekly Influenza Update) 
• Washington State Department of Agriculture: Avian Influenza in Livestock and Pets 
• CDC: H5 Bird Flu: Current Situation 
• CDC: Signs and Symptoms of Bird Flu in People 
• CDC: Interim Guidance on the Use of Antiviral Medications for Treatment of Human Infections with Novel Influenza A Viruses Associated with Severe Human Disease  

 Contact:

 To report suspected cases or for any other questions, please contact: 

Snohomish County Health Department
425-339-3503
shd-cdquestions@co.snohomish.wa.us