US Reports First-Ever Human Case of H5N5 Avian Influenza

US Confirms First Human Infection With H5N5 Bird Flu

The United States has confirmed the world’s first human case of the H5N5 subtype of avian influenza , marking a significant event in global infectious disease surveillance. The patient—an older adult with existing medical conditions—was hospitalised in early November after showing symptoms resembling avian influenza. Laboratory testing by federal and state health agencies verified the infection as H5N5, a strain previously detected only in birds and select animal species.

Detection and Initial Investigation

Preliminary diagnostic tests identified influenza A H5 , prompting further subtype analysis that confirmed H5N5 . The individual maintained a backyard flock that had probable exposure to wild birds, making animal-to-human transmission the most likely source. Health authorities continue to trace the exact exposure route while monitoring close contacts as a precautionary measure.

Understanding Avian Influenza Viruses

Avian influenza viruses circulate widely among wild aquatic birds , the natural reservoirs of Influenza A. These viruses can spill over into domestic poultry and occasionally infect humans. Subtypes are identified through combinations of hemagglutinin (H) and neuraminidase (N) proteins, resulting in strains such as H5N1, H7N9, H5N8 and now H5N5. Some forms are low pathogenic, while others are highly pathogenic and can cause severe outbreaks in birds.

Why H5N5 Raises Concern

Although the current public-health risk remains low, scientists are monitoring the situation because H5 viruses mutate rapidly and can undergo genetic reassortment, potentially producing variants capable of greater spread. Any instance of a bird-only virus infecting humans is considered a warning signal for global health preparedness.

Transmission, Symptoms and Preventive Measures

Human infection generally occurs through close contact with infected birds , contaminated dust or surfaces. Symptoms range from fever and cough to severe respiratory distress. Health authorities advise avoiding sick poultry, using protective equipment when handling birds, and practising strict hygiene.

Exam-Oriented Facts

• H5N5 had never been detected in humans before this case.

• Avian influenza strains are classified by H and N proteins .

• Wild aquatic birds are the natural reservoirs of Influenza A.

• Transmission usually occurs via unprotected contact with infected birds .