Epidemiology is the branch of medicine that studies the factors related to the spread of disease in large numbers of people. It deals with the causes, distribution patterns and control of diseases. The idea of epidemiology is based on the observation that certain environmental and personal characteristics are related to the occurrence of diseases. The study concentrates on both non-communicable and communicable diseases and the information gathetion and control strategies and as a tool in managing and treating patients who are already suffering from a particular disease.

Philosophers and social critics like Plato and Jonathan Swift pointed out that the main cause of diseases is human luxury. However, it is Hippocrates who is credited as being the father of epidemiology and as the first person to have established a link between environmental factors and the occurrence of diseases in humans. The Greek doctor was, in fact, responsible for coming up with the terms epidemic (affects a large number of people) and endemic (prevalent in a particular area) diseases.

Epidemiologists collect and analyze data to determine the origin or cause, method of spread, and ways of prevention and control of a particular disease.