Epidemiology is defined as the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.
Epidemiology is the study of what makes people sick.
But it's different than being a doctor or physician. Epidemiology looks at sickness on a population scale. So, to many people, epidemiologists are people that study epidemics. To an extent, that's true. The epidemiologist here at the Hartford Health Department is called on when an epidemic takes place in Hartford.