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27th April 2022 (8 Topics)

First human case of H3N8 bird flu

Context

China has recorded the first human infection with the H3N8 strain of bird flu.

About

What's happening?

  • A four-year-old boy from central Henan province was found to have been infected with the variant after developing a fever and other symptoms.
  • The H3N8 variant has previously been detected elsewhere in the world in horses, dogs, birds and seals but no human cases of H3N8 have been reported.

Why it matters?

  • It's the first time the virus has jumped from animals to humans but it looks like a one-off jump and further risk of spread is low.
  • Many different strains of bird flu are present in China and some sporadically infect people, usually those working with poultry.
  • Last year China reported the first human case of H10N3.

Bird Flu:

  • Bird flu, or avian flu, is an infectious type of influenza that spreads among birds. In rare cases, it can affect humans.
  • There are lots of different strains of bird flu virus. Most of them don't infect humans. But there are 4 strains that have caused concern in recent years:
    • H5N1 (since 1997)
    • H7N9 (since 2013)
    • H5N6 (since 2014)
    • H5N8 (since 2016)

How bird flu spreads to humans?

  • Bird flu is spread by close contact with an infected bird (dead or alive).
  • This includes:
    • touching infected birds
    • touching droppings or bedding
    • killing or preparing infected poultry for cooking
    • Markets where live birds are sold can also be a source of bird flu.

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.
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