Influenza, Avian


  • Categorized according to the ability to kill chickens in a laboratory setting:
    • Highly pathogenic avian influenza (HPAI):
      • Influenza (H5N1), avian first detected in Chinese geese in 1996
      • Occasional human pathogen since 1997
        • Since 2003, the WHO has reported 860 H5N1 human avian influenza cases in 19 countries (mostly SE Asia), with a mortality rate of ~50%.
        • H5 avian influenza infection in man from Colorado (CDC, April 2022) with direct poultry exposure; extensive avian influenza among poultry flocks and wild birds in N. America in 2021-2022.
    • Low pathogenic avian influenza (LPAI):
      • Most influenza A H5 types (except H5N1 as above)
        • H5N6 may be an exception; WHO has 36 cases reported to date in 2021, with 21 deaths.
      • Most influenza A H7 types
        • H7N9 (2013-14, 2016-17 China) appears to cause severe human infection (mortality rate ~40%).
        • Types H7N2, H7N3, and H7N7 cause mild-moderate occasional human infection
      • H9N2 (rare human illness, mild), 100 people since 1998, predominantly SE Asia, Egypt, the Arabian peninsula, India, Pakistan and Senegal.
      • H6: one human infection in Taiwan (2013)
      • H10: three occurrences since 2004 in humans (Egypt, Australia, China)
  • CDC (2021): considers risks for outbreaks of HPAI H5 or H7 viruses in poultry or wild birds as low.

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Last updated: March 6, 2023