Epidemiology has been defined as the study of the distribution and determinants of disease and injury in human populations. Epidemiologists study the variation of disease in relation to age, sex, race, occupational and social characteristics, place of residence, susceptibility, exposure to specific agents or other pertinent characteristics. Also of concern are the temporal distribution of disease, the examination of trends and cyclical patterns of disease, and intervals between exposure to causative factors and onset of disease.
Epidemiology is an exciting field with constantly expanding boundaries. The range of activities considered epidemiology include investigation and control of disease outbreaks, study of environmental and industrial hazards, evaluation of new preventive or curative clinical treatments, determination of the health needs of populations, and evaluation of effectiveness of prevention strategies and health services.