Epidemiology

The chapter will introduce the principles and practice of epidemiology. It begins by defining epidemiology and related definitions such as outbreaks, epidemics and pandemics. It outlines the history of epidemiology including the work of Hippocrates, John Graunt and Dr John Snow and explains some of the most common measures of disease and death such as mortality and morbidity rates. It discusses how epidemiologists try to establish ‘cause and effect’, by identifying associations between health exposures and outcomes such as diseases. The chapter describes observational and experimental epidemiological research study designs with some of their strengths and limitations. These include cross-sectional studies, case reports and case series, ecological studies, cohort studies, case control studies, clinical trials and community trials. Finally, the chapter discusses screening tests and the concepts of sensitivity, specificity, positive predictive value and negative predictive value as one example of the many nuances that need to be considered when presenting epidemiological data.