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: (i) homosexual/bisexual men, (ii) blood transfusion recipients, (iii) intravenous drug users, or (iv) heterosexuals. Our model consists of a system of 4N differential equations (d.e.s). We sho w that as N --> infinity, the number of infectives in each community conver ges to the unique solution of a Liouville type stochastic differential equa tion (s.d.e.). (C) 2000 Elsevier Science Ltd. All rights reserved.