Introduction to Epidemiology
Objective: To understand the basic concepts of epidemiology and to examine how infections spread among populations.
Problem Definition: What is Epidemiology?
A. Basic Concepts and Principles:
Epidemiology is the branch of science that deals with the study of the dynamics of health and ill health in populations.
To unravel the dynamics of health, epidemiology is concerned with the patterns of occurrence and distributions of events that affect health. The patterns of occurrence should be critically examined in terms of frequencies and probabilities of the events that affect health either over time (dynamic) or at a particular point in time(static). This latter reference to health at a point in time is somewhat artificial in that time is a continuous process. Let us briefly examine these concepts.
The healthy state lies along a continuum of health on one side and ill health on the other. Along this path, various states of health such as those of marginal nature could be identified. It is then merely for convenience that one classifies the states as healthy or unhealthy; the point being that health is relative and all facets should be considered.
Along this continuum of health, various determinants affect the dynamics of health (and disease). A determinant can be any factor, whether event, characteristic or other definable entity that brings about change (positive or negative) in a health condition. Thus an understanding of the determinants of health and the mechanisms of how and at what level these determinants operate to affect health (disease) is a vital component of epidemiology.