Basic Concepts of Epidemiology
Many concepts of epidemiology such as incidence or prevalence of a disease, mortality and risk factors have already appeared in previous chapters. Their meaning was sufficiently clear to allow a preliminary discussion of the basic principles of epidemiology, of its role in public health and of the main issues in the epidemiology of infectious diseases but a rigorous definition was missing. Without rigorous definitions, however, it is impossible to conduct epidemiologic studies of any value. Hence we are now going to state the main definitions while restricting ourselves to the fundamental ones and not entering into the many ramifications that exist.