India has reported its first case of human infection with avian influenza A(H9N2) virus, detected in a four year old in West Bengal, the World Health Organization said.

This is the second human infection of avian influenza A(H9N2) notified to WHO from India, the first being 2019. “Further sporadic human cases could occur as this virus is one of the most prevalent avian influenza viruses circulating in poultry in different regions,” the multi-lateral agency added.

The patient was discharged on May 1, from the hospital with oxygen support, the WHO said, adding that the patient had an exposure to poultry at home and its surroundings. However, there were no known persons reporting symptoms of respiratory illness in the family, the neighbourhood, or among healthcare workers at health facilities attended by the case at the time of reporting, it added.

According to the International Health Regulations (2005), a human infection caused by a novel influenza A virus subtype is an event that has the potential for high public health impact and must be notified to the WHO. “Most human cases of infection with avian influenza A(H9N2) viruses are exposed to the virus through contact with infected poultry or contaminated environments.”

With the available evidence, WHO assesses the current public health risk posed by this virus as low, it added.

WB incident

Giving details on the WB infection, the WHO said it received a notification from the IHR National Focal Point regarding a human case of avian influenza A(H9N2) virus infection in West Bengal on May 22, 2024.

The child previously diagnosed with hyperreactive airway disease, initially presented to the paediatrician with fever and abdominal pain on January 26, 2024. Outlining the disease progression, the note said, over the month the child developed seizures, persistence of respiratory distress, high-grade fever etc and was re-admitted to the pediatric ICU and intubated.

“On March 5, a nasopharyngeal swab was sent to the Kolkata Virus Research and Diagnostic Laboratory and tested positive for influenza A (not sub-typed) and rhinovirus. The same sample was sent to the National Influenza Centre at the National Institute of Virology in Pune for subtyping. On April 26, the sample was sub-typed as influenza A(H9N2) through a real-time polymerase chain reaction,” the WHO said.

Zoonotic viruses

Animal influenza viruses normally circulate in animals but can also infect humans, primarily through direct contact, the note explained.

“Depending on the original host, influenza A viruses can be classified as avian influenza, swine influenza, or other types of animal influenza viruses,” it said.

While the Indian government has not made any statement on this yet, the WHO said, the Government had implemented , among other things, a team composed of a public health specialist, a paediatrician, and veterinary officials from the Animal Husbandry Department and Veterinary College, and the Government of West Bengal to investigate the occurrence of influenza-like illness (ILI) in local poultry.

The WHO further advised people to avoid unprotected contact with live poultry, high-risk environments such as live animal markets or farms, and surfaces that might be contaminated by poultry droppings.

 Avian influenza virus infections cause diseases ranging from mild upper respiratory tract infection to more severe diseases and can be fatal. Conjunctivitis, gastrointestinal symptoms, encephalitis and encephalopathy have also been reported.