The field of epidemiology deals with the study of distributions, causes, prevention, and the control of acute and chronic diseases in populations. Disease is not randomly distributed. Instead, it occurs more often among people and groups with certain shared characteristics.
Epidemiologists seek to learn why, how, and when some people contract diseases when others do not. The answers to these questions are necessary for monitoring the health status of a population, for developing new medical treatments and disease prevention efforts, and for providing an evidence base to health care and policy leaders. For these reasons, epidemiology is considered a cornerstone of public health practice.