‘H9N2’

Indian scientists have detected the country’s first case of infection with a rare variant of the virus that causes avian influenza, or bird flu. 

What is H9N2?

• H9N2 is a subtype of the influenza A virus, which causes human influenza as well as bird flu.
• The H9N2 subtype was isolated for the first time in Wisconsin, the US in 1966 from turkey flocks. According to the US National Centre for Biotechnology Information (NCBI), H9N2 viruses are found worldwide in wild birds and are endemic in poultry in many areas.
• However, they are somewhat neglected.
• H9N2 viruses could potentially play a major role in the emergence of the next influenza pandemic.
• According to the World Health Organization (WHO), with avian influenza viruses circulating in poultry, there is a risk for sporadic infection and small clusters of human cases due to exposure to infected poultry or contaminated environments.
• Therefore, sporadic human cases are not unexpected.

How it has infected humans?

• H9N2 virus infections in humans are rare, but likely under-reported due to typically mild symptoms of the infections.
• Cases of human infection have been observed in Hong Kong, China, Bangladesh, Pakistan, and Egypt. One case was detected in Oman recently.
• The first case globally was reported from Hong Kong in 1998.
• A total of 28 cases in China have been reported since December 2015. Cases continue to be reported mainly from mainland China and Hong Kong.
• The virus has, however, spread extensively among poultry populations. Surveillance for influenza viruses in poultry in Bangladesh during 2008-2011 found H9N2 virus to be the predominant subtype.
• The virus was also identified in poultry populations in surveillance studies in Myanmar during 2014-16 and Burkina Faso in 2017.
• In India, the virus was picked up in February 2019 during a community-based surveillance study in 93 villages of Korku tribes in Melghat district of Maharashtra.

Understanding Influenza:

• The World Health Organization (WHO) defines influenza as “a contagious, acute respiratory illness caused by influenza viruses, usually influenza A or B subtypes.”
• Influenza, also known as the flu, is a viral respiratory illness that can spread when a person with the infection sneezes or coughs and droplets travel to another person's nose or mouth.
• The influenza virus, which causes the illness, is of four types: A, B, C, and D.
  • Influenza A: An influenza A virus has two surface proteins:
    • Hemagglutinin (H)
    • Neuraminidase (N)
  • Influenza B: Influenza Bviruses can also cause seasonal epidemics that typically only affect humans. There are two lineages of influenza B:
    • Victoria
    • Yamagata
  • Influenza C: Influenza C viruses cause mild illnesses — they do not appear to cause epidemics.
  • Influenza D: Influenza D viruses mainly affect cattle and do not seem to infect humans.