New prospects for epidemiologic investigations.

Epidemiology has evolved from its historic origins as the study of major epidemics and vital statistics to a contemporary focus on the study of the distribution and determinants of health and disease in humans. This evolution reflects changes in the patterns of diseases and deaths that have occurred in our time and has placed new emphasis on preventing avoidable, premature deaths. Advances in clinical medicine, laboratory science, statistical and data handling methods, and in our basic understanding of the pathogenesis of disease have enabled epidemiologists to better examine causes of disease and to propose more effective strategies for prevention and control.