ABSTRACT
This chapter describes the role of epidemiology in establishing the status of diseases in populations, the burden that diseases constitute for human populations, and how diseases spread. Epidemiology was originally considered as a branch of medical science that deals with epidemics. The application of epidemiological findings to the control and prevention of health problems is a natural extension of epidemiology. The field covered by epidemiology has been broadened to include the study of the distribution and determinants of accidents and of genetic and physiological conditions in human populations as well as infectious processes. Descriptive epidemiology concerns the occurrence of diseases, and their causative agents, in time, place, and population. Analytical epidemiology examines and tests associations or hypothesized causal relationships. The epidemiological investigation provides the opportunity to collate information about cases which are temporally related and may as a result reveal the cause, route of transmission, and host and environmental factors associated with the outbreak.
