First Human Case of H5N5 Avian Influenza Confirmed in the United States

On November 14, 2025, the Washington State Department of Health confirmed the first human case of H5N5 avian influenza in the United States. The patient, an older adult with underlying health conditions from Grays Harbor County, remains hospitalized. This marks the first known human infection with the H5N5 strain, though similar strains like H5N1 have previously infected humans.

While the H5N5 strain has been detected in animals, this is the first instance of human infection. Health officials, including the Centers for Disease Control and Prevention (CDC), currently assess the risk to the general public as low. The patient maintains a backyard flock of domestic poultry that had exposure to wild birds, which is believed to be the source of infection.

Background on Avian Influenza and H5N5

Avian influenza, commonly known as bird flu, is caused by influenza A viruses that primarily affect birds but can infect humans. Human infections are rare and usually result from direct or indirect exposure to infected birds or contaminated environments.

H5N5 is a subtype of the H5 family of avian influenza viruses. While it has been detected in animals, this is the first known human infection with this strain. The H5 family also includes H5N1, which has previously infected humans and is known for its potential to cause severe disease.

Historical Context

Prior to this case, the most recent human infection with avian influenza in the U.S. was reported in February 2025. Between 2024 and early 2025, approximately 70 human cases of H5N1 were reported in the U.S., primarily among farm workers, with most cases resulting in mild illness.

Globally, between January 1 and August 4, 2025, 26 human infections with H5N1 were detected, resulting in 11 deaths. All infections were in individuals with likely or reported direct contact with poultry or wild birds.

Public Health Response

The CDC and the Washington State Department of Health currently consider the risk to the public from avian influenza to be low. However, individuals who work with or have contact with infected birds or other potentially infected animals are at higher risk and should take precautions, including wearing personal protective equipment (PPE).

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. People with backyard poultry are advised to avoid contact with sick or dead birds and report illness to the Washington State Department of Agriculture.

Social and Societal Implications

The confirmation of a human case of H5N5 avian influenza may raise public concern about the potential for a broader outbreak. Clear communication from health officials is essential to inform the public about the low risk and preventive measures.

The detection of avian influenza in a backyard flock highlights the importance of biosecurity measures in both commercial and backyard poultry operations to prevent the spread of the virus.

Conclusion

The confirmation of the first human case of H5N5 avian influenza in the United States is a significant event in public health. While the risk to the general public remains low, this case underscores the importance of vigilance, biosecurity measures, and prompt public health responses to emerging infectious diseases.