Epidemiology is a computer model that simulates the spread of an infectious disease through a population. This program allows users to graphically enter population and disease characteristics (e.g., the virulence of the pathogen, the likelihood of transmission), to set up an initial population, and then observe the changes in population characteristics and the prevalence of the disease through time. Using modified SIR-type models (Susceptible-Infected-Recovered), Epidemiology allows students to ask a variety of “what if?” questions, to design and perform their own investigations, and to explore the implications of various public health policies. The direct-manipulation, graphical interface encourages exploration, and makes the program accessible to introductory students. Nevertheless, the simulation model is capable of addressing problems that even graduate students in population biology or public health should find interesting and challenging.
An Epidemiology simulation is based on a model defined by the Define Model dialog box. For example, if you wish to model a disease in which there is an asymptomatic stage when an individual is first infected (as with AIDS or rabies), one can choose the appropriate check box from the “Define Model...” dialog box. The model choices available allow you to use Epidemiology to study the dynamics of a large variety of diseases.
The population characteristics that influence population growth and the spread of a disease in the population are summarized in the Flow Chart window. The flow chart gives a graphical depiction of the way that the models underlying Epidemiology work
.Values for factors such as the birth rates, death rates, and disease transmission rates, can be viewed and/or changed by clicking on the appropriate button on the flow chart. Results are displayed in three types of windows: (1) the Status window, (2) the Population Size vs Time window, and (3) the Deaths vs Time window. These windows are updated every display interval. The Status window displays the current time and the number of individuals in the total population and in each category. The Population Size vs Time window (shown below) displays a graph of the number (or proportion) of individuals in different population categories through time. The Deaths vs Time window displays the number of individuals dying each time interval. It displays both the number of “natural” deaths, and the number dying from the disease.
New Features in Version 2.5
Added ability to model infectious diseases that are transmitted by vectors (e.g., mosquitoes, fleas), or that affect other populations (reservoir populations) besides the host (e.g., rats, monkeys).
Macintosh and Power Macintosh