The spread of AIDS among interactive transmission groups

We consider the spread of an AIDS epidemic among N interacting communities (cities, say), each having at least one of the major four HIV transmission groups: 1. mosexual/bisexual men, lood transfusion recipients, intravenous drug users, or eterosexuals. odel consists of a system of 4N differential equations (d.e.s). We show that as N → ∞, the number of infectives in each community converges to the unique solution of a Liouville type stochastic differential equation (s.d.e.).