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- 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)
- 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)
- 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
- Vaccine (H5N1) for adults 18 to 65 years of age has been approved.
- Consider antiviral chemoprophylaxis if H5N1 is circulating in the community; no postexposure chemoprophylaxis recommended for H7N9 if the individual meets travel exposure criteria
Commonly Associated Conditions
Severe respiratory distress (common in severe cases)