Epidemiology: the foundation of public health

Epidemiology is the basic science of public health, because it is the science that describes the relationship of health and/or disease with other health-related factors in human populations, such as human pathogens. Furthermore, epidemiology has been used to generate much of the information required by public health professionals to develop, implement, and evaluate effective intervention programmes for the prevention of disease and promotion of health, such as the eradication of smallpox, the anticipated eradication of polio and guinea worm disease, and the prevention of heart disease and cancer. Unlike pathology, which constitutes a basic area of knowledge, and cardiology, which is the study of a specific organ, epidemiology is a philosophy and methodology that can be applied to learning about and resolving a very broad range of health problems. It is not enough to know what the various study designs and statistical methodologies are. The ‘art’ of epidemiology is knowing when and how to apply the various epidemiological strategies creatively to answer specific health questions. The uses and limitations of the various epidemiological study designs are presented in this chapter to illustrate and underscore the fact that the successful application of epidemiology requires more than a knowledge of study designs and epidemiological methods. These designs and methods must be applied appropriately, creatively, and innovatively if they are to yield the desired information. The field of epidemiology has been expanding dramatically over the last three decades, as epidemiologists have demonstrated new uses and variations of traditional study designs and methods (Pearce, 2012). We can anticipate that the scope of epidemiology will expand even more in the future as increasing numbers of creative epidemiologists develop innovative new strategies and techniques. The chapters in this section present detailed discussions of the principles and methods of epidemiology. In this introductory chapter, I will attempt to define epidemiology, to present ways in which epidemiology is used in the advancement of public health, and finally, to discuss the range of applications of epidemiological methodologies. What is epidemiology? There are many definitions of epidemiology, but every epidemiologist will know exactly what it is that he or she does. Defining epidemiology is difficult primarily because it does not represent a body of knowledge, as does, for example,