infectivity potential (Kanki et al., 1994). Consistent with the idea that HIV-2 may be less virulent than HIV-1 and may have been present in West Africa for many decades, seropositivity increases with age. Among prostitutes in Dakar, Senegal, almost 100 percent of those aged 50 and over are infected with HIV-2 (Marlink, 1994).
The disparity in the speed with which HIV-1 and HIV-2 are spreading is particularly striking in Abidjan, Côte d'Ivoire, where HIV-1 has become by far the predominant virus, causing a major epidemic of AIDS. In contrast with HIV-1, HIV-2 has barely increased in Abidjan during the past 6 years (Figure 3-8). This finding suggests that under identical conditions and among populations with the same behavior, HIV-2 is less readily transmissible through sexual intercourse than HIV-1. Nevertheless, studies in Côte d'Ivoire and The Gambia have found that HIV-2 infection correlates with factors associated with HIV-1 infection, such as prostitute contact, history of past STDs, and past and current genital ulcer disease. In Côte d'Ivoire and Guinea-Bissau, 40 percent of spouses of people with HIV-2 were also infected.