US Reports World's First Human Case Of H5N5 Bird Flu. All About The Virus

A US man has become the first person infected with the H5N5 strain of bird flu, health officials said last week. The patient, an older adult with underlying health conditions, was hospitalised in early November with symptoms of avian influenza, the Washington State Department of Health confirmed.

Subsequent testing identified the virus as influenza A H5, and further analysis determined it was the H5N5 subtype, a strain previously detected only in animals or birds and never before in humans.

The individual keeps a mixed backyard flock of domestic poultry that had been exposed to wild birds, health officials said. Either the domestic flock or the wild birds are considered the most likely source of infection, though investigators are still working to determine how the exposure occurred.

What Is Avian Influenza?

Avian influenza, or “bird flu,” is a disease caused by Influenza A viruses that typically infect birds, as per the Centers for Disease Control and Prevention (CDC). These viruses are naturally found in wild aquatic birds, which act as reservoirs.

Virus Subtypes

Influenza A viruses are categorised by their surface proteins: hemagglutinin (H) and neuraminidase (N). There are many subtypes, for example, A (H5) viruses include H5N1, H5N5, H5N8, etc.

Some strains are classified as low pathogenic (LPAI), causing mild disease in birds, while others are highly pathogenic (HPAI) and can kill large numbers of birds rapidly.  

Why Is H5N5 A Concern?

Influenza A (H5) viruses are genetically diverse and can reassort (shuffle genetic material), which means new variants may emerge, as per the World Organisation for Animal Health.

While the current risk is low, “pandemic potential” requires vigilance particularly in animal populations where these viruses circulate.

How It Spreads

In birds, the virus spreads through respiratory secretions and feces. Humans typically get infected through close, unprotected contact with infected birds or contaminated environments (eg, poultry farms, live bird markets).

Transmission can occur via droplets, dust, or by touching surfaces contaminated with bird secretions and then touching one's eyes, nose, or mouth, as per the World Health Organization.

Symptoms In Humans

Symptoms can range from none (asymptomatic) or mild to very severe.

Common symptoms include fever, cough, sore throat, shortness of breath, fatigue, muscle aches, and sometimes gastrointestinal issues like vomiting or diarrhea.

Eye symptoms (conjunctivitis) have been reported, as per Johns Hopkins Medicine.

Severe cases can lead to pneumonia, acute respiratory distress, or death, reports the Pan American Health Organization.

Prevention

• Avoid close contact with sick or dead birds.
• Use appropriate protective gear (masks, gloves) when handling poultry or cleaning bird coops.
• Avoid raw or undercooked poultry, meat, eggs, and raw milk from infected animals.

Public health agencies recommend ongoing surveillance and rapid detection of new human infections.