Definition of epidemiology

The study of the occurrence and distribution of health-related states or events in specified populations, including the study of the determinants influencing such states, and the application of this knowledge to control health problems

The primary "knowledge object" of epidemiology as a scientific discipline is causes of health-related events in populations. In the past 70 years, the definition has broadened from concern with communicable disease epidemics to take all processes and phenomena related to health in populations

Therefore epidemiology is much more than a branch of medicine treating epidemics

International Epidemiological Association. A Dictionary of Epidemiology (ed. Porta M). Oxford: Oxford University Press, 5th edition, 2008

Study involves surveillance, observation, hypothesis testing, analytic research, and experiments

Distribution refers to the analysis by time, place, and classes or subgroups of persons affected in a population or in a society

Determinants are all the physical, biological, social, cultural, economic, and behavioural factors that influence health

Health-related states and events include diseases, causes of death, behaviours, reactions to preventive programmes, and provision and use of health services

Specified populations are those with common identifiable characteristics

Application to control ... makes explicit the aim of epidemiology: to promote, protect, and restore health