Infectious Disease Book

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Avian InfluenzaAka: Avian Influenza A, Bird Flu, Asian H5N1, H5N1

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  1. See Also
    1. Influenza
  2. Background
    1. Historical Avian Influenza Outbreaks
      1. Spanish Flu (H1N1): 1918-1919 (40-100 Million deaths)
      2. Asian Flu (H2N2): 1957 (2 million deaths)
      3. Hong Kong Flu (H3N2): 1968 (1 million deaths)
    2. Recent strains
      1. Asian strain (H9N2): 1998
      2. Netherlands (H7N7):2003
    3. Avian Influenza A (H5N1, Bird flu)
      1. Currently active Avian Influenza Strain
      2. Expected to be next Influenza pandemic
      3. 1997: 18 cases (6 deaths) in Hong Kong
      4. 2004-5: 137 cases (70 deaths) Southeast Asia, China
        1. Outbreak associated with more virulent Z-strain
      5. 2006: 228 cummulative cases and 130 deaths
        1. Total cases thought to be much higher
        2. Mild cases are likely underestimated
  3. Pathophysiology
    1. Life-cycle of Avian Influenza A
      1. Avian Influenza A shed in waterfowl (esp. ducks)
      2. Poultry and pigs become infected
      3. Animal handlers become infected
        1. Exposure to infected animals is primary source
        2. Human-to-human transmission requires high exposure
    2. Virulence
      1. Immune reaction to virus is intense
      2. Results in cytokine storm
  4. Risk Factors: Exposures
    1. Asian poultry animal handlers
    2. Asian animal markets, poultry farms, cock fights
    3. Cleaning up areas with poultry feces present
    4. Contact with fertilizer contaminated with bird feces
  5. Symptoms: Onset 2-5 days after exposure
    1. Fever
    2. Cough
    3. Respiratory distress (associated with Viral Pneumonia)
    4. Watery Diarrhea
  6. Diagnosis: Pharyngeal swab for H5-Specific RNA
    1. Preferred over nasal swab
    2. Detection by Reverse transcriptase PCR
  7. Labs
    1. Complete Blood Count with Leukopenia
  8. Imaging
    1. Chest XRay
      1. Nonspecific infiltrates by 7 days post-fever onset
  9. Management
    1. Tamiflu
      1. See Neuraminidase Inhibitors (also Relenza)
      2. Treatment: 75 mg PO bid for 5 days
        1. Must be started within 48 hours of onset
        2. Reduces illness severity by 40%
      3. Post-exposure prophylaxis: 75 mg PO qd x7-10 days
      4. Resistance rates are currently low
    2. Other anti-viral agents
      1. Amantadine and Ramantadine resistance is high
    3. Other experimental agents
      1. Statins
        1. May reduce cytokine storm reaction
        2. Improves survival in septic shock
        3. Only effective if started prior to infection
  10. Prevention
    1. Avoid exposure
      1. See Risk Factors above
    2. H5N1 Vaccine
      1. Undergoing human trials
      2. Not expected to be available for several years
  11. Resources
    1. CDC Avian Flu Information
      1. http://www.cdc.gov/flu/avian/gen-info/facts.htm
    2. WHO Avian Influenza information
      1. http://www.who.int/csr/don
    3. U.S. Department of Health and Human Services
      1. http://www.pandemicflu.gov
  12. References
    1. Fauci (2006) Emerg Infect Dis 12:73
    2. Juckett (2006) Am Fam Physician 74(5):783
    3. Monto (2005) N Engl J Med 352:323

Influenza in Birds (C0016627)

Definition (MSH)Infection of domestic and wild fowl and other BIRDS with INFLUENZA A VIRUS. Avian influenza usually does not sicken birds, but can be highly pathogenic and fatal in domestic POULTRY.
Definition (CSP)infection caused by influenza A viruses that occur naturally in birds; wild birds can carry the viruses, but usually do not get sick from them; some domesticated birds, including chickens, ducks, and turkeys, can become infected, often fatally; one strain of avian influenza, the H5N1 virus, may infect various types of animals, including wild birds, pigs, and tigers; symptoms in birds and other animals vary, but virulent strains can cause death within a few days; human H5N1 infection was first recognized in 1997 in Hong Kong.
ConceptsDisease or Syndrome (T047)
EnglishAvian Flu, avian flu virus, Avian influenza, Avian Influenzas, Bird flu, bird flu virus, Fowl Plague, Influenza in Bird, Influenza in Birds
Spanishgripe aviaria, influenza aviaria, peste de las aves de corral
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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