E3 Easy Epidemiology for Everyone

Indiana Epidemiology Newsletter
August 2007

E3is a new feature of the Indiana Epidemiology Newsletter dedicated to exploring the fundamentals of epidemiology  Each month, a different epidemiology concept will be explored to enhance understanding of basic epidemiology.


“Whoever wishes to investigate medicine properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces for they are not at all alike, but differ much from themselves in regard to their changes”

Hippocrates, 400 B.C.E

This quote from Hippocrates represents the very foundations of modern epidemiology. “Epidemiology” is derived from the Greek words, epi (upon) + demos (people) + logy (study of). (The word epidemic has similar roots.) Epidemiology is recognized as the basic science of public health. The textbook definition of epidemiology is “the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems” (Last, p 62. 2001). Epidemiology draws on many different disciplines in an effort to describe cause-and-effect relationships and is responsible for directing public health action (Dicker, 2002).

Like other sciences, public health epidemiology is based on a scientific method. Inthis case, the method, as outlined below, should be thought of as the natural, logical steps taken when “doing” epidemiology.

Step Purpose

Data gathering, often ongoing, to monitor the level of disease in a population

Descriptive epidemiology

Categorizing and displaying data to better understand aspects of a specific disease or condition

Analytic epidemiology

If differences appear between groups in the descriptive data, further analysis can help determine if the differences are real and if certain groups are at greater/less risk for the outcome of interest


Based on the findings of the analysis, actions can be taken to positively influence the health outcome of interest


Follow-up to determine if the intervention was effective

One of the basic premises of epidemiology is that “disease doesn’t occur randomly, but rather in distinct patterns that reflect the operation of underlying factors” (Friis and Sellers, p 108., 1999). It is in these patterns that we need to look, and the monthly E3 topics over the next year will demonstrate how this is accomplished.

There have been many successes attributed to epidemiology—the most famous is Dr. John Snow’s removal of the pump handle on a drinking water pump on Broad Street in London in the midst of a cholera epidemic in 1854. More recent examples exist in infectious disease control; cancers; cardiovascular disease, in particular the Framingham study; and advances in maternal and child health. Epidemiology is the very cornerstone of public health science.