ABSTRACT
The purpose of this chapter is to provide an introduction to the difference equation perspective often found useful by epidemiologists as they work to understand the spread of a disease in a population. After a brief discussion of the purposes of epidemiology, we will develop both the nomenclature and the difference equations used to predict the number of patients with a disease under a mix of interesting and useful assumptions. These equations will be well recognized by the advanced worker as immigration models, emigration models, birth models, and death models, and will be so labeled in this chapter. The next chapter will be a continuation of this work from the difference equation perspective for more complex models that perhaps more realistically portray changes in the numbers of patients with an illness. In each of these developments, the focus here will be to elaborate the role of difference equations in providing solutions to these dynamic systems.
