Because of the similar virological properties of HIV types 1 and 2, HIV-2 was assumed to be as infectious and capable of inducing AIDS as HIV-1. Seroepidemiological studies have shown significant rates of HIV-2 infection in West Africa, and surveys from other regions of the world indicate that the spread of HIV-2 infection continues. However the pathogenic potential of HIV-2 is considered to be lower than that of HIV-1. It is therefore important to understand the transmission properties of HIV-2 and its contribution to the AIDS pandemic. Since 1985, we have prospectively studied 1452 registered female prostitutes in Dakar, Senegal, with sequential evaluation of their antibody status to HIV-1 and HIV-2. During the study the overall incidence of HIV-1 and HIV-2 was the same (1.11 per 100 person-years of observation [pyo]). However, the annual incidence of HIV-1 increased substantially: there was a 1.4-fold increased risk per year and thus a 12-fold increase in risk over the entire study period. The incidence of HIV-2 remained stable, despite higher HIV-2 prevalence. In our population the heterosexual spread of HIV-2 is significantly slower than that of HIV-1, which strongly suggests differences in the viruses' infectivity potential.
PIP: Between February 1985 and February 1993 in Dakar, Senegal, the Social Hygiene Clinic screened 1452 registered female prostitutes (5608 samples) for sexually transmitted diseases, including HIV-1 and HIV-2. The overall prevalence rate stood at 11.3% for HIV-2 while it was 6.2% for HIV-1. 12 women (0.8%) tested positive for HIV-1 and HIV-2. Health workers followed the 1277 women who were initially HIV seronegative to determine seroconversion. 46 of these women seroconverted to HIV-2 and another 46 seroconverted to HIV-1. Overall incidence of HIV-2 and HIV-1 was 1.11 per person years of observation (pyo). Eight women (incidence = 0.19 per 100 pyo) seroconverted to both HIV-2 and HIV-1. When the researchers controlled for age, nationality, years of registered prostitution, calendar year, and time in study, the relative risk for HIV-2 infection each year did not change. On the other hand, there was a significant 1.43 annual increase in the risk for HIV-1 infection (p .002), indicating a 12-fold increase in the risk of HIV-1 infection over the study period. These findings suggest that the 2 viruses have a distinctly different in-vivo biology and that HIV-2 has a lower infectivity than does HIV-1.