Epidemiology Health Article

EPIDEMIOLOGY

Epidemiology is the indispensable basic science of public health. It provides the logical framework for the facts that enable public health officials to identify important public health problems and to delineate their dimensions. Epidemiologic methods are used to define these health problems; to classify, identify, and elucidate their causes; and to plan and evaluate rational control measures.

HISTORICAL DEVELOPMENT OF EPIDEMIOLOGY

In ancient times, epidemics and plagues were terrifying natural phenomena that cried out for a more rational explanation than that they were due to the wrath of god or the machinations of evil spirits. Hippocrates (c. 460–377 B.C.E.) described many kinds of epidemics and in On Airs, Waters, Places and other writings. He offered empirical insights into environmental and behavioral factors that might be associated with certain kinds of disease. Although doctors and others engaged in the healing arts did not clearly understand the concept of contagion until several hundred years later, Fracastorius (c. 1478–1553) identified several ways that infections can be transmitted—by direct contact, by what we now call droplet spread, and by contaminated clothing.

The science of epidemiology took root with empirical observations of epidemics and other causes of death. John Graunt (1620–1674), in London, complied the first mortality tables on England's bills of mortality. Statistical analyses of deaths due to childbed fever by Ignaz Semmelweiss (1818–1865) in Vienna in the early nineteenth century and of tuberculosis by Pierre Charles Alexandre Louis (1787–1872) in Paris demonstrated the power of numbers. In London, in 1848 and 1854, meticulous, logical examination of the facts and figures about cholera epidemics by John Snow (1813–1858) revealed the mode of communication of this deadly epidemic disease. Snow is regarded as the founder of modern epidemiology because of his use of such careful methods.

Until early in the twentieth century almost all epidemiology focused on communicable diseases, although Percivall Pott's (1714–1788) observations on cancer of the scrotum in chimney sweeps and James Lind's dietary experiment with fresh fruit to prevent scurvy (1975) were precursors of modern noncommunicable disease epidemiology and clinical trials, respectively. The use of epidemiology in studies of coronary heart disease and cancer in large-scale trials of many new preventive and therapeutic regimens, in nationwide surveys of health status, and in evaluation of health services came to the fore in the second half of the twentieth century. In the final quarter of the twentieth century, powerful computers, information technology, and more rigorous methodological approaches transformed epidemiology and made it a mandatory feature of clinical science as well as the most fundamental basic science of public health.