Effects of contact structure on the transient evolution of HIV virulence
Fig 2
Schematic representations of models with explicit contact structure. Top row (a,b) shows models with instantaneous partnership formation; bottom row (c,d) shows those where individuals remain single for some period of time between partnerships. Left column (a,c) shows models with within-partnership transmission only; in these models transmission can only occur within serodiscordant partnerships, and serodiscordant partnerships can only be formed by dissolution and reformation of partnerships. Right column (b,d) shows models that allow extra-pair and uncoupled transmission. Solid arrows represent infection transitions; dotted arrows represent partnership dissolution and formation; dashed arrows show influences on infection rate, including both within-pair transmission (blue) and extra-pair/uncoupled transmission (red). In addition to these models, we also use random-mixing and implicit models with only S and I compartments and heterogeneous models where each compartment is subdivided by sexual activity rate (of both partners, in the case of partnership compartments).