About WH

WH is a modeling framework for the simulation of disease spread in randomly mixing populations. WH operates at the level of the individual animal, and incorporates sources of individual-level variation such as variability in the durations of incubating and infectious periods, the stochastic nature of disease spread among individuals, the effects of vaccination, and disease mortality.

WH extends modeling concepts used previously (e.g., Abbey, 1952; Perez et al., 2002, Bates et al., 2003; Carpenter et al., 2004). These earlier models are either deterministic, or draw a single value from each individual-level distributions and apply those same values to every individual within an iteration of the model: that is, these earlier models treat all individuals as though they are completely equivalent. By constrast, in WH, all parameters related to disease spread, durations of disease states, and effects of vaccination are applied to each individual, so that the variablility among individuals is more realistically represented.

Obtaining and installing WH

WH is open source software and is released under the terms of the GNU General Public License. The current version, and to date the only public release, of WH is version 0.9.7. This is the first version that fully implements all of the capabilities described in the resources listed below. New versions will be posted here as they are released.

An executable version of WH for Microsoft Windows is currently available. Installation of WH should be straight-forward, and takes only a few steps. Simply download the most recent installation package for WH from the link below. Once you have saved the installation package to your computer, double-click its icon to perform the installation. Follow the on-screen prompts if you wish to change any of the default installation options.

  • Download the installation package for WH version 0.9.7:
    Installer icon WHSetup-0_9_7.exe (5.8 MB)


The following forms of additional documentation for WH are available:

Source code

WH is written in Delphi Version 7, Professional Edition. While it may be possible to compile the interface with other versions of Delphi, no others have been tested. Source code for WH 0.9.7 is available below. In addition, please see the list of required libraries for NAADSM/PC: the same libraries are required for WH.

References cited

Abbey, H., 1952. An examination of the Reed-Frost theory of epidemics. Hum. Biol. 24, 201-233.

Bates, T.W., Thurmond, M.C., Carpenter, T.E., 2003. Description of an epidemiologic simulation model for use in evaluating strategies to control an outbreak of foot-and-mouth disease. Am. J. Vet. Res. 64:195-204.

Carpenter, T.E., Thurmond, M.C., Bates, T.W., 2004. A simulation model of intraherd transmission of foot and mouth disease with special reference to disease spread before and after clinical diagnosis. J. Vet. Diagn. Invest. 16:11-16.

Perez, A.M., Ward, M.P., Charmandarian, A., Ritacco, V., 2002. Simulation model of within-herd transmission of bovine tuberculosis in Argentine dairy herds. Prev. Vet. Med. 54:361-372.

Reeves, A., Talbert, M., Salman, M.D., Hill, A.E., in preparation. Development of a stochastic, individual-based modeling framework for within-unit transmission of highly infectious animal diseases.