Stephen J. Schueler, M.D.

Influenza Underlying Cause

Influenza is caused by a virus that infects the lungs, throat and nasal passages.

Influenza comes in 3 basic viral types, but each type can have many more subtypes, referred to as strains.

The three types of influenza include:

  • Influenza A:
    • Most common type
    • H1N1 strain has recently become very common
    • H5N1 or bird flu is less commonly seen strain of influenza A
    • Causes severe symptoms
  • Influenza B:
    • Second most common type
    • Causes less serious symptoms
  • Influenza C:
    • Uncommon cause for influenza
    • Causes mild symptoms

Continue to Influenza Transmission

Last Updated: Dec 16, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Influenza References
  1. Centers for Disease Control and Prevention (CDC)
  2. Ebell MH, White LL, Casault T. A systematic review of the history and physical examination to diagnose influenza. J Am Board Fam Pract. 2004 Jan-Feb;17(1):1-5. [15014046]
  3., HHS Interagency Public Affairs Group on Influenza Preparedness and Response
  4. Jefferson T, Smith S, Demicheli V, Harnden A, Rivetti A, Di Pietrantonj C. Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet. 2005 Feb 26-Mar 4;365(9461):773-80. [15733718]
  5. Montalto NJ. An office-based approach to influenza: clinical diagnosis and laboratory testing. Am Fam Physician. 2003 Jan 1;67(1):111-8. [12537174]
  6. Strategy for Off-Site Rapid Triage(c) (SORT) and Real-time Epidemiological Assessment for Community Health(c) (REACH), Emory University, Principal Investigators: Alexander Isakov, MD, MPH; Arthur Kellermann, MD, MPH, Collaboration with the Emory at Grady Health Literacy Team (Ruth Parker, MD; Kara Jacobson, MPH, CHES; Lorenzo DiFrancesco, MD)
  7. VHA Office of Public Health Surveillance and Research; Influenza Algorithm Work Group
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