Epidemiology is the study of distribution and determinants of disease.
Epidemiologists study sick and well people to determine the crucial difference between those who get disease and those who are spared. Epidemiology weighs and balances, contrasts and compares Epidemiologists use rates. An epidemic occurs when there are significantly more cases of the same disease than past experience would have predicted. Ask questions about person, place, time. One now famous Cholera epidemic in 1854 led to the discovery of the mode of communication of Cholera.