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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.

Impact2009 v 1.0

October 27, 2009, 1:00 PM ET

Laboratory-confirmed infections with 2009 H1N1 influenza represent only a fraction of total cases in a population.  Persons with influenza may not be included in reported counts for several reasons, including not all ill people seek medical care and have a specimen collected, not all specimens are sent to a public health laboratory for confirmatory laboratory testing, and not all specimens will give positive test results because of the timing of collection or the quality of the specimen. 

Impact2009 is a spreadsheet-based model which estimates the total human health burden of 2009 H1N1 influenza in a population by adjusting the total number of known laboratory-confirmed cases and hospitalizations with H1N1 in a population for these sources of under-detection.  The results calculated by the model include overall and age-specific estimates of the total number of cases, hospitalizations and deaths from H1N1 that occurred in a specified population. 

This spreadsheet is a companion to the estimates presented in the manuscript entitled “Estimates of the Prevalence of Pandemic (H1N1) 2009, United States, April–July 2009” by Reed et al. to be published in the December 2009 issue of the journal Emerging Infectious Diseases. 

Using this spreadsheet, the user can specify the size and age distribution of the population of interest and the number and age distribution of reported cases of 2009 H1N1 influenza.  The user may also vary the range of values for the parameter estimates used in the original model, including:  medical care seeking, specimen collection, submission of specimens for confirmation, laboratory detection of influenza, and reporting of confirmed cases.  

System Requirements:

  • Windows* operating system (MS Windows 2000 or newer)
  • Microsoft Excel (MS Office 2000 or newer)
  • 486 Pentium processor and at least 128MB RAM
  • 2 MB of hard drive storage space

* MS Windows and Office is a copyrighted product produced by Microsoft Corporation, WA.  Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.

Instructions for Downloading:

Before loading and starting Impact2009, you must change Excel's security level.
You must first do the following steps:

  1. Open a blank Excel spreadsheet.
  2. Click Tools and then click Macro, choose Security
  3. Set Security Level to Medium.
  4. Click OK.
  5. Double click and open Impact2009 file.
  6. When asked to Disable Macros or Enable Macros, click Enable Macros.

Downloading the Files:

* We recommend downloading and saving the Impact2009 spreadsheet to your computer, then open the spreadsheet from your computer. This will allow the spreadsheet to open in Excel instead of your web browser.

Download Impact2009 v1.0 Software Now

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