This chapter focuses on the myriad ways in which one can model contacts between individuals. The two most important aspects of contacts for infection transmission are (1) the number of contacts per unit of time, and (2) the number of different individuals with whom these contacts occur. Aspect 1 is concerned not only with variation in the number of transmission opportunities during a pairing, but also with the duration of the pairing. Aspect 2 concerns spatial or social networks with variation in the set of potential “contactees.” This could be the entire population, a dynamic subset of the population, or a fixed subset of the population. The remainder of the chapter discusses the new aspects that arise in heterogeneous populations where different types of individuals are recognized; consistency conditions; populations that consist of very many small groups, like a community of households, with intense within-group contact; graphs and networks; and the pair approximation technique.
From Geometries to Contact Graphs
