Epidemiology deals with the incidence, prevention and control of diseases within certain populations. This is not restricted to infectious diseases. In fact, the link between cancer and tobacco use is one of epidemiology's primary concerns. The distinction between epidemiological research and other branches of medicine lies predominantly in its method rather than in its subject matter. Epidemiologists conduct studies on a large-scale, using predominantly human subjects. These studies track their subjects over a long period of time, to see which people contract disease and which ones stay disease-free. The next step is to figure out what factors are common to those who got sick, or those who remained healthy. One focus of epidemiology is on keeping the public informed about how clinical studies actually affect their lives, i.e. what are the risk factors for a disease? What information needs to be distributed in order to make a difference in terms of disease prevalence?
Epidemiology is closely linked to issues about how medical information is represented in the media, and the ethical issues that underlie this representation.