Second case of H9N2 Virus detected in India: 4-year-old in West Bengal tests positive, public health risk deemed low

WHO said that available epidemiological and virological evidence suggests that this virus has not acquired the ability to sustain transmission among humans.

BySumit Jha

Published Jun 12, 2024 | 3:33 PM Updated Jun 12, 2024 | 9:57 PM

H9N2 Virus in India

On Tuesday, 11 June, the World Health Organization (WHO) confirmed that India has reported a case of H9N2 influenza virus in India.

This is the second human infection of avian influenza A(H9N2) reported to WHO from India, with the first case occurring in 2019.

On 22 May 2024, the International Health Regulations (IHR) National Focal Point (NFP) for India reported a case of human infection with avian influenza A(H9N2) virus to the World Health Organization (WHO).

The infection was detected in a four-year-old child residing in West Bengal.

WHO stated that the child has recovered and was discharged from the hospital.

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Potential for significant public health risk

According to the IHR (2005), a human infection caused by a novel influenza— A virus subtype is an event with the potential for significant public health impact and must be notified to WHO.

“Most human cases of infection with avian influenza A(H9N2) viruses are due to exposure to the virus through contact with infected poultry or contaminated environments. Human infection generally results in mild clinical illness,” said the WHO.

WHO further added that based on available information, further sporadic human cases could occur since this virus is one of the most prevalent avian influenza viruses circulating in poultry in different regions.

However, with the currently available evidence, WHO assesses the current public health risk to the general population posed by this virus as low.

The risk assessment, however, will be reviewed, should further epidemiological or virological information become available.

Globally, there have been some hospitalised cases and two fatal cases reported in the past. Given the continued detection of the virus in poultry populations, sporadic human cases can be expected.

Currently, available epidemiological and virological evidence suggests that this virus has not acquired the ability to sustain transmission among humans.

Therefore, the likelihood of human-to-human spread is low.

Timeline of the case

26 January: The four-year-old patient was previously diagnosed with hyperreactive airway disease and was initially presented to the paediatrician with fever and abdominal pain.

29 January: The patient developed seizures and was brought to the same paediatrician.

1 February: The patient was admitted to the paediatric intensive care unit (ICU) of a local hospital due to the persistence of severe respiratory distress, recurrent high-grade fever and abdominal cramps.

The patient was diagnosed with post-infectious bronchiolitis caused by viral pneumonia.

2 February: The patient tested positive for influenza B and adenovirus at the Virus Research and Diagnostic Laboratory at the local government hospital.

28 February: The patient was discharged from the hospital.

3 March: With a recurrence of severe respiratory distress, he was referred to another government hospital and was admitted to the paediatric ICU and intubated.

5 March: 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 then sent to the National Influenza Centre at the National Institute of Virology in Pune for subtyping.

26 April: The sample was sub-typed as influenza A(H9N2) through a real-time polymerase chain reaction.

1 May: The patient was discharged from the hospital with oxygen support. Information on the vaccination status and details of antiviral treatment were not available at the time of reporting.

The patient had exposure to poultry at home and in the surroundings. 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.

Animal influenza viruses

Animal influenza viruses normally circulate in animals but can also infect humans. Infections in humans have primarily been acquired through direct contact with infected animals or through indirect contact with contaminated environments.

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

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

Laboratory tests are required to diagnose human infection with influenza. WHO periodically updates technical guidance protocols for the detection of zoonotic influenza using molecular methods.

Also Read:Union Health Ministry deploys high-level team to take stock of bird flu in Kerala

Public health response

WHO said that it is providing continued support to the Government of India through technical advice, updates on risk assessment and updating contingency plans— both in the human and animal sectors in line with the global guidance.

Meanwhile, the Government of India has implemented the following coordination activities in response to the incident:

  • 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 was constituted to investigate the occurrence of influenza-like illness (ILI) in local poultry.
  • Surveillance of ILI in humans was enhanced in the reporting district and neighbouring areas.
  • The District Veterinary Department enhanced surveillance of animals.
  • The Animal Husbandry Department will share information regarding the surveillance of avian influenza viruses (all subtypes under surveillance) in poultry, wild birds, etc., in the affected and adjoining areas with State Health authorities and at the central level with the Ministry of Health and Family Welfare, Government of India.

(Edited by Sumavarsha Kandula)