First Human Case of H5N5 Bird Flu Confirmed in the US

Washington, Nov 19, 2025: In a concerning announcement, health officials in the US have confirmed the first-ever case of H5N5 bird flu in a human, a strain that was previously identified only in avian species. The patient, a senior with pre-existing health issues, was hospitalized in early November after showing symptoms associated with avian influenza.

The Washington State Department of Health has verified that initial tests identified the virus as Influenza A H5, with subsequent analysis confirming the rare H5N5 subtype. This marks the first documented human infection globally, raising alarms among healthcare professionals and virology experts.

Source of Infection
The patient has been in contact with a mixed flock of domestic poultry, which had potential exposure to wild birds, according to officials. Investigators are exploring whether the domestic birds or contact with wild birds served as the source of the infection. Authorities are continually monitoring the situation to pinpoint the exact mode of transmission.

Understanding H5N5 and Bird Flu
Avian influenza, widely recognized as bird flu, stems from Influenza A viruses commonly found in wild aquatic birds. These viruses are categorized by their hemagglutinin (H) and neuraminidase (N) proteins, giving rise to various subtypes, including H5N1, H5N8, and now H5N5.

Some strains are classified as low pathogenic and result in mild illness in birds, while highly pathogenic variants can rapidly devastate bird populations. The emergence of H5N5 in humans highlights the virus's capacity for mutation and adaptation, underscoring the need for ongoing global vigilance.

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

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

Preventive Measures and Global Concern
Global health organizations are advising the public to avoid direct contact with sick or deceased birds, utilize protective equipment when handling poultry, and ensure thorough cooking of poultry and eggs. Surveillance and prompt detection are vital to avert wider outbreaks and to monitor the virus for any possible human-to-human transmission.

Chris Green, executive director of the Animal Health and Pandemic Preparedness Alliance, emphasized: “While the risk to the general public remains relatively low, the discovery of H5N5 in a human signifies the ongoing threat posed by zoonotic viruses. Vigilant monitoring and stringent biosecurity measures are crucial to prevent additional infections.”

This first human case of H5N5 in the US comes amid ongoing concerns regarding the pandemic potential of avian influenza strains. Health authorities around the world are reassessing biosecurity protocols at poultry farms and live bird markets to ensure effective response strategies are established to mitigate the spread of this rare yet alarming virus.

As investigations progress, officials stress the importance of public readiness, hygiene, and careful handling of domestic birds as proactive measures against future human infections.