US Reports First Human Case of H5N5 Bird Flu

Washington, Nov 19, 2025: In an alarming development, US health officials have confirmed the first-ever human case of H5N5 bird flu, a strain previously detected only in birds and animals. The patient, an older adult with underlying health conditions, was hospitalized in early November after exhibiting symptoms of avian influenza.

The Washington State Department of Health confirmed that initial testing identified the virus as Influenza A H5, and further analysis revealed the rare H5N5 subtype. This marks the first known human infection globally, raising attention among public health authorities and virologists.

Source of Infection
The patient maintains a mixed backyard flock of domestic poultry, which had been exposed to wild birds, according to health officials. Investigators suspect either the domestic flock or contact with wild birds as the likely source of the infection. Authorities continue to monitor the situation closely to determine the exact mode of transmission.

Understanding H5N5 and Bird Flu
Avian influenza, commonly known as bird flu, is caused by Influenza A viruses that naturally circulate in wild aquatic birds. These viruses are classified based on their hemagglutinin (H) and neuraminidase (N) proteins, producing multiple subtypes like H5N1, H5N8, and now H5N5.

Some strains are low pathogenic, causing mild illness in birds, while highly pathogenic strains can decimate bird populations rapidly. H5N5’s emergence in humans underscores the virus’s potential to mutate and adapt, emphasizing the importance of global vigilance.

Transmission and Symptoms
Bird flu viruses can spread through respiratory secretions, feces, or contaminated environments. Human infections typically occur through close, unprotected contact with infected birds or their droppings.

Symptoms in humans can range from mild to severe and may include fever, cough, sore throat, shortness of breath, fatigue, muscle aches, vomiting, diarrhea, and conjunctivitis. Severe cases may escalate to pneumonia, acute respiratory distress, or even death.

Preventive Measures and Global Concern
Health agencies worldwide urge the public to avoid direct contact with sick or dead birds, use protective gear when handling poultry, and thoroughly cook all poultry and eggs. Surveillance and rapid detection are critical to prevent wider outbreaks and to monitor the virus for any potential human-to-human transmission.

Chris Green, executive director of the Animal Health and Pandemic Preparedness Alliance, emphasized: “While the risk to the general population remains low, the emergence of H5N5 in a human highlights the ongoing threat of zoonotic viruses. Continued monitoring and strict biosecurity measures are essential to prevent further infections.”

The first human H5N5 case in the US comes amid ongoing concerns about the pandemic potential of avian influenza strains. Health authorities worldwide are now reviewing biosecurity protocols in poultry farms and live bird markets, ensuring rapid response plans are in place to limit the spread of this rare but concerning virus.

As investigations continue, officials emphasize public awareness, hygiene, and careful handling of domestic birds as the first line of defense against future human infections.