The superior physician helps before the early budding of the disease. (Huang Ti)

This chapter aims to describe epidemiology and its role in public health. The chapter begins with a brief history of epidemiology, and then goes on to discuss how disease occurrence is measured and how the burden of disease is quantifi ed. We then look at the common sources of data for public health research, provide an overview of epidemiological study designs and conclude with an example of research being translated into public health action by looking at a case study of alcohol harm reduction in Hong Kong.