China, Vietnam and India have reported seven cases of infection among children and adults so far this year
The World Health Organization (WHO) has confirmed a case of avian influenza, commonly known as bird flu, in a four-year-old child from West Bengal, India. This marks the second human infection with a H9N2 strain of bird flu reported in India since 2019.
The child has recovered and was released from the hospital after treatment.
The WHO confirmed the low pathogenic avian influenza (LPAI) A (H9N2) virus in a statement dated June 11, 2024. The International Health Regulations National Focal Point (NFP) for India reported the case on May 22, 2024.
The virus most likely infected the child through exposure to poultry at home or in the surrounding environment. The WHO has assessed the public health risk from the virus as low.
LPAI A (H9N2) is different from the highly pathogenic avian influenza A (H5N1), which is widely reported to cause outbreaks in poultry and US cattle.
The WHO statement noted the child had a history of hyperreactive airway disease and initially visited a paediatrician with fever and abdominal pain on January 24. On January 29, the patient reported seizures and returned to see the same paediatrician.
By February 1, the child’s condition had deteriorated to the point where he was admitted to a nearby hospital’s intensive care unit (ICU) with persistent severe respiratory distress, recurring high-grade fever and abdominal cramps.
The patient was later diagnosed with post-infectious bronchiolitis as a result of viral pneumonia. Medical tests at the local government hospital’s virus research and diagnostic laboratory revealed that the patient had influenza B and adenovirus infections.
On February 28, the patient was discharged from the hospital following his recovery.
However, on March 3, the patient experienced severe respiratory distress and was transferred to another government hospital, where they were admitted to the paediatric ICU and intubated.
On March 5, a nasopharyngeal swab was sent to the Kolkata Virus Research and Diagnostic Laboratory, which tested for influenza A and rhinovirus. At that time, the virus subtype had not been identified.
On April 26, the same sample was tested using a real-time polymerase chain reaction (PCR) and found to be LPAI A (H9N2).
In May, the patient was released from the hospital with assisted oxygen support.
No other people familiar with the patient, including family members, neighbours and healthcare workers, reported any signs of respiratory illness.
WHO warned that additional sporadic human cases may occur because the virus is widespread and prevalent among avian influenza viruses in poultry populations across different regions.
The Indian government has formed a team of public health specialists, a paediatrician and veterinary officials from the Animal Husbandry Department and Veterinary College, along with the Government of West Bengal, to investigate the occurrence of influenza-like illness in local poultry, the WHO statement added.
It has also directed the monitoring of influenza-like illnesses in humans in the reporting district and surrounding areas. The district veterinary department has started monitoring animals and the animal husbandry department has been asked to share information on possible avian influenza virus subtypes in wild birds and poultry in the affected area.
The WHO stated that, while most cases of human infection result in mild clinical illness, two deaths have been reported in the past.
In addition to India, more cases were reported from China and Vietnam earlier this year, between June 2 and June 8.
The virus was first detected in humans in Vietnam on April 9. A 37-year-old patient from Tien Giang Province who was admitted to intensive care on March 21 tested positive for LPAI A (H9N2) using PCR.
The WHO suspects that the patient contracted the virus while living near a poultry market and witnessing daily poultry trade in front of his home.
“There have been no reports of dead or sick poultry near the patient’s residence or of consumption of sick, dead, or uncooked poultry products from his household or neighbouring households,” the WHO stated.
According to a report published by the Centre for Health Protection, Hong Kong, a three-year-old boy from Guangxi Zhuang Autonomous Region in Mainland China was detected with the LPAI A (H9N2) virus.
Four other cases of children infected with the same virus subtype were reported from Guangxi Zhuang Autonomous Region, Anhui Province, Jiangxi Province and Guangdong Province.
In Hong Kong Special Administrative Region, a 22-month-old girl was also reportedly infected with the virus subtype on February 15.
According to United States’ Centers for Disease Control and Prevention, LPAI A (H9N2) viruses have been reported sporadically in more than 100 people since 1998 in China and in Hong Kong, Bangladesh, Cambodia, Egypt, India, Oman, Pakistan and Senegal.
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