II. Definitions

  1. Influenza-Like Illness (ILI)
    1. Documented fever >37.8 C. or (>100 F) and-or
    2. Cough and Sore Throat
    3. Absence of another cause

III. Epidemiology

  1. Reported April 12, 2009 in Veracruz, Mexico and WHO declared pandemic by April 27, 2009
    1. (2009) N Engl J Med 361:674-9 [PubMed]
  2. Widespread Influenza in United States in September, 2009
    1. Peak this early is unprecedented (previously outbreaks started in October and November)
  3. Global pandemic declared over as of August 2010
  4. United States H1N1 outcomes
    1. Cases: 61 million infected
    2. Hospitalizations: 274,000
    3. Deaths: 12,470

IV. Pathophysiology

  1. Chimera of swine flu, avian flu, and human flu
  2. Transmission through respiratory droplets (coughing, sneezing, or contaminated fomites)

V. Labs

  1. Standard rapid Influenza A and B testing only has 70% Test Sensitivity at best
    1. Treat outpatient cases empirically without testing
  2. Hospitalized case testing
    1. Test with Rapid Influenza Testing and
    2. Viral culture and
    3. Send sample to Department of Public Health (process varies by state)

VI. Management

  1. Indications to use specific agents (e.g. Tamiflu) as soon as possible (do not wait for labs)
    1. All patients hospitalized for Influenza-like illness
    2. Patients at high risk of complication from Influenza-like illness
    3. Prophlyaxis for patients at high risk of complication with close exposure to contact with H1N1
      1. Use treatment protocol instead of prophylaxis if exposure was >48 hours ago
      2. Do not give prophylaxis to healthy patients without risk
    4. Treatment and prophylaxis may be started by phone for patients who meet criteria
  2. Quarantine
    1. Stay home for 7 days from onset or at least 24 after last fever, significant symptoms

VII. Prevention

  1. H1N1 Immunization
  2. Prevent transmission
    1. Isolate patient early in triage process and have them wear mask
    2. Modified Droplet Precautions
      1. Healthcare workers wear mask with shield, gloves, gown
      2. N95 required only for aerosol generating procedure (e.g. intubation), but not nebulizer
      3. Pregnant healthcare workers should not take care of H1N1 patients
    3. Patients should still be considered infectious even after completing antiviral agents (i.e Tamiflu)

VIII. Prognosis: Risks of mortality

  1. Highest risk ages
    1. Under age 5 years (especially under age 1 years)
    2. Age 45-54 years old
  2. Pregnant women (highest risk in third trimester)
  3. Corticosteroid use has been associated with a higher mortality risk

IX. References

  1. Kline (2009) UMN CME Internal Medicine Review, Minneapolis

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Ontology: Novel H1N1 influenza (C2712889)

Concepts Disease or Syndrome (T047)
English Novel H1N1 influenza, (Novel) 2009 influenza H1N1, (Novel) 2009 H1N1 influenza NOS