Figure 1
From: Treating cofactors can reverse the expansion of a primary disease epidemic
(a) two-patch SI model and (b) four-patch cofactor model diagrams. (a) The two-patch SI model appearing in Anderson et. al. (1988) [18], upon which the four-patch cofactor model in (b) is built, and (b) The four-patch cofactor model. Dotted lines represent transitions related to the cofactor condition; solid lines represent transitions related to the primary disease infected population. Curved lines begin and end at the subpopulations from and to which a transition is occurring, and pass near the interacting population which causes the transition.