Correlation between historical lack of male circumcision and the epidemic emergence of HIV-2

Background: Epidemic HIV-2 emerged in humans twice (groups A and B), both circa 1930. Its closest ancestors are SIVsmm infecting sooty mangabeys from southwest Ivory Coast. The earliest serological surveys of HIV-2 in West Africa (1987–91) show a patchy spread with only Ivory Coast and Guinea-Bissau having mature epidemics by then. Methods: We estimated past male circumcision rates of 209 West African ethnic groups, based on an ethnographic literature review. Uncertainty was incorporated by defining plausible ranges of parameters (e.g. timing of introduction, proportion circumcised). We generated 1000 sets of past circumcision rates per city using Latin Hypercube Sampling with different parameter combinations. We explored the correlation between early HIV-2 prevalence and estimated circumcision rate (both logit-transformed). A credible confidence interval for the correlation was constructed using 500 bootstrap replicates. Results: Demographic and Health Surveys show that male circumcision is nowadays almost universal throughout the region. However, our ethnographic review reveals that, in early 20th century, many ethnic groups did not practice it, or did it late in life. Our estimates for circumcision rates in 1950 are, for Bissau: 80–85%; Abidjan: 50–57%; Bouaké: 56–63%; Monrovia: 79–84%; the major cities of Senegal, Gambia, Guinea, and Sierra Leone had >90%. HIV-2 prevalence in 1987–91 and circumcision rate in 1950 were correlated (r=-0.463; 95% CI: -0.726–-0.213; p=0.017). In addition, southwestern Ivory Coast and neighboring Liberian areas were inhabited by non-circumcising ethnic groups (in 1930) heavily exposed to SIVsmm through bushmeat. Conclusions: The differential HIV-2 spread between West African countries correlates with different historical circumcision rates in their main cities. We suggest HIV-2 only formed early substantial foci in low circumcision rate cities. Lack of male circumcision in rural areas exposed to bushmeat may have had a role in boosting the chances of successful SIV zoonosis.status: publishe