Avian Flu



  • Human infection due to avian influenza type A viruses (subtypes H5N1 and H7N9 to date). H5N1 is highly pathogenic; H7N9 has low pathogenicity.
  • Presents with influenza-like illness and (primarily) lower respiratory tract symptoms
  • High mortality rate in elderly and very young (particularly H5N1)
  • Synonym(s): bird flu, H5N1, H7N9



  • >860 confirmed human cases A(H5N1) (53% fatality rate); most cases from Egypt and Indonesia
  • 1,564 cases and 610 deaths A(H7N9) (mostly from China) since February 2013
  • Predominant age: affects all age groups


Etiology and Pathophysiology

  • Infected poultry (domesticated ducks, turkeys, chickens) reservoir
  • Low incidence of human-to-human transmission, typically household clusters and health care workers
  • Incubation period: 7 days (range 2 to 17 days)

Risk Factors

  • Known direct contact with H5N1 or H7N9 virus or infected individual
  • Contact with infected poultry
  • Recent travel to endemic country (within 10 days of symptom onset)

General Prevention

  • Consider isolating any patient with influenza-like symptoms who has had close contact with H5N1, H7N9, or ill poultry.
  • Respiratory droplet precautions and N-95 masks
  • There is an approved vaccine (H5N1) for adults 18 to 65 years of age.
  • Consider antiviral chemoprophylaxis if H5N1 is circulating within the community; no postexposure chemoprophylaxis is recommended for H7N9 if travel exposure criteria are fulfilled.

Commonly Associated Conditions

Severe respiratory distress (common in severe cases)

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