ABSTRACT
The use of mathematical models in the analysis of the spread of infectious diseases goes back to pioneering works by Ross (1911) and by Kermack and McKendrick (1927), and has developed into a very rich body of theories and applications, as shown for instance in the monographs by Bailey (1975) and Anderson and May (1991). The goals of mathematical modelling may be very diverse: Hethcote and Van Ark (1992) list fifteen purposes, and three limitations, of epidemiological modelling. At one extreme, one may study simple and general models in order to identify the main mechanisms that underlie the epidemic dynamics, and to define concepts and quantities, such as the ‘basic reproductive ratio’ (Diekmann, Heesterbeek and Metz, 1990), that crucially determine the final outcome of an epidemic. At the other extreme, one may build a very detailed model for the spread of a specific disease in a specific population in order to predict accurately the future trends.
