Avian Influenza

In News

• Recently, China reported the first human case of H3N8 bird flu.

H3N8

• H3N8 viruses originated in horses and then transmitted to dogs. 
• H3N8 equine influenza (horse flu) viruses have been known to exist in horses for more than 40 years. 
• Scientists say that the virus jumped from horses to dogs for survival and has adapted to cause illness in dogs and spread among dogs, especially those housed in kennels and shelters.
• The H3N8 bird flu virus was first detected in North American waterfowl in 2002, however, no cases of human transmission were reported until now.

Avian Influenza or Bird Flu

• Type of Virus: 
  • Avian influenza or bird flu refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses. 
  • Influenza A virus causes influenza in birds and some mammals, and is the only species of the genus Alpha-influenza-virus of the virus family Orthomyxoviridae. 
  • Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon.
• Spread: 
  • These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. 
• Human Transmission: 
  • Bird flu viruses do not normally infect humans. However, sporadic human infections with  bird flu viruses have occurred. 
• Virus shedding: 
  • Infected birds can shed avian influenza A viruses in their saliva, nasal secretions, and faeces. 
  • Susceptible birds become infected when they have contact with the virus as it is shed by infected birds. 
  • They also can become infected through contact with surfaces that are contaminated with virus from infected birds.
• Common Symptoms: 
  • Cough, fever, sore throat, muscle aches, headache, and shortness of breath. 
  • They may also develop life-threatening complications like pneumonia, pinkeye (conjunctivitis), respiratory failure, kidney dysfunction, and heart problems.
• Treatment: 
  • Antiviral treatment functions best if one receives it as soon as the symptoms emerge. 
  • However, it noted that antiviral drugs may not work as well against some A(H5N1) and A(H7N9) bird flu viruses.

Different types of avian influenza

• Avian Influenza (AI) type A viruses are divided into subtypes based on two proteins on the surface of the virus:
  • Hemagglutinin (HA), of which there are 16 subtypes (H1-H16)
  • Neuraminidase (NA), of which there are 9 subtypes (N1-N9)
• Many combinations of HA and NA proteins are possible (i.e., H5N1, H5N2, H7N2, H7N8, etc).
• AI viruses are also classified into two groups based on their ability to produce disease in chickens: 
  • highly pathogenic avian influenza (HPAI) or 
  • low pathogenic avian influenza (LPAI).
• HPAI viruses cause high mortality in poultry and occasionally high death rates in certain species of wild birds.
• LPAI viruses can cause a variety of outcomes in poultry ranging from no apparent clinical signs to moderate death rates. LPAI viruses usually cause little to no signs in wild birds.
• H5 and H7 LPAI viruses have the potential to mutate or evolve into HPAI viruses and are closely monitored by animal health officials.
• Most avian influenza:
  • The H5N1 and H7N9 strains of bird flu are the primary reason for the most number of avian influenza cases in humans. 
  • The former was first detected in 1997 whereas the latter emerged in 2013 and has been responsible for most cases of human illness from avian influenza.

Status in India

• Earlier, the first recorded human death due to the bird flu in India happened.
• Earlier, bird flu was confirmed in several states with thousands of birds, including migratory species, being found dead.

Measures against bird Flu

• Revised Action Plan for Prevention, Control & Containment of Avian Influenza (2021)
• Opting Culling method
• Cleansing and disinfecting and reduction of people’s movement. 
• Vaccination to humans: Avian Influenza vaccine is available outside India e.g. the USA has developed the vaccine for Human infection.

Source: IE