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Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

NOTE:This page is not intended as a stand-alone Web document and is intended to serve merely as a Section 508-accessible version of the PowerPoint presentation "2009 H1N1: Overview of a Pandemic, April 2009 - August 2010."

2009 H1N1: Overview of a Pandemic

Preparing for a Pandemic

Preparing for a Pandemic

  • Pandemics are sporadic, unpredictable
  • Caused by novel influenza A viruses
  • Spread from person to person and cause human illness
  • Most of the population is susceptible

Three conditions must be met for a pandemic to start:

  1. A new influenza virus subtype must emerge for which there is little or no human immunity;
  2. It must infect humans and causes illness; and
  3. It must spread easily and sustainably (continue without interruption) among humans


  • The threat of an avian influenza A (H5N1) pandemic shaped some assumptions
    • pandemic virus would likely emerge in birds, not swine
    • pandemic virus would likely emerge in Southeast Asia, not North America
  • Planned for a worst case scenario – Severity of 1918, not 1968
  • Planning for a severe pandemic provided opportunities to improve epidemiology and laboratory capacity
    • Better lab and epidemiologic surveillance
    • New reporting requirements by WHO and CDC

Actions for Diagnostic Preparedness

  1. Develop New Diagnostic Tests and Improved Diagnostic Capabilities
  2. Improve Surge Capacity
  3. Implement Proficiency Testing
  4. Increase Laboratory Training
  5. Develop Policy and Regulatory Preparedness
  6. Improve Access to Viruses and Reagents
  7. Provide Guidance for Clinicians
  8. Improve Virologic Surveillance
  9. Conduct Antiviral Resistance Testing

Enhanced Laboratory Detection

Developed New Diagnostic Tests

Image of LightCycler Device, AB 7500 Device and a Mesoscale Diagnostics device
  • 2007 - PCR Test for detecting avian influenza A (H5) viruses on "LightCycler"
  • 2008 - PCR Test for detecting A, B, H1, H3, and H5 on "AB 7500"
  • 2008 - Experimental Point of Care Test on "Mesoscale Diagnostics" device

Enhanced Virus Surveillance

  • Increased number of labs in US with testing devices, staff, and reagents
  • Increased number of specimens being tested
  • Developed "Influenza Reagent Resource"
    • Contract laboratory to manufacture and distribute PCR reagents during routine seasons
    • Rapidly makes reagents during a pandemic surge

Increasing Detection of Swine Influenza

  • Increasing numbers of cases of swine influenza being detected NEJM 2009 Shinde et al.
    • Due to increased public health laboratory testing
    • Few number of cases
      • 1-2 per year until 2005
      • 11 total from 2006 to Feb 2009
    • Limited transmission among cases
    • Most with some connection to swine exposure
  • Increasing efforts among government agencies in U.S. to investigate human cases of swine flu

Next: Detection of 2009 H1N1 Virus >

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