December 10, 2023

H5N1 Avian Influenza

Syllabus– General Studies 3(Science and Technology)


Recently, the first recorded death due to the bird flu (H5N1 avian influenza) was in Delhi, India in 2021.

Bird flu: the disease

  • Bird flu or avian influenza is a disease caused by avian influenza Type A viruses found naturally in wild birds worldwide. The virus can infect domestic poultry including chickens, ducks, turkeys and there have been reports of H5N1 infection among pigs, cats, and even tigers in Thailand zoos.
  • Avian Influenza type A viruses are classified based on two proteins on their surfaces –
    • Hemagglutinin(HA) and
    • Neuraminidase(NA).
  • There are about 18 HA subtypes and 11 NA subtypes. Several combinations of these two proteins are possible e.g., H5N1, H7N2, H9N6, H17N10, etc.


Infection in Humans

  • There have been reports of avian and swine influenza infections in humans including A(H1N1), A(H1N2), A(H5N1), A(H7N9), etc.
    • The first report of human H5N1 infection was in 1997 and currently, over 700 human cases of Asian Highly Pathogenic Asian Avian Influenza A (HPAI) H5N1 virus have been reported to the World Health Organisation from 16 countries.
    • The infection is deadly as it has a high mortality rate of about 60%.


  • The most common route of virus transmission is direct contact — when a person comes in close contact with infected birds, either dead or alive.
  • Humans can also be affected if they come in contact with contaminated surfaces or air near the infected poultry. There is no sufficient evidence suggesting the spread of the virus through properly cooked meat.


Symptoms of avian influenza infection:

According to US CDC, the reported signs and symptoms of avian influenza A virus infections in humans have ranged from mild to severe influenza-like illness.

  • Fever, cough, sore throat, muscle aches, nausea, abdominal pain, diarrhea, vomiting
  • Severe respiratory illness (e.g., shortness of breath, difficulty breathing, pneumonia, acute respiratory distress, viral pneumonia, respiratory failure)
  • Neurologic changes (altered mental status, seizures)

Risk group:

  • Children and adults below 40 were seen to be the most affected and mortality was high in 10-19 years olds.

Human to Human Transmission:

  • The human-to-human transmission of the H5N1 virus was very rare.
  • The transmission of the virus from birds to humans is rare and sustained human-to-human transmission of the H5N1 virus has not yet been established.


Question-What are the major types of avian influenza? Also write a sort note on basic symptoms of the disease.


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