Sex Transm Infect 87:640-645 doi:10.1136/sextrans-2011-050174
  • AIDS 2031
  • Original article

Attempting to explain heterogeneous HIV epidemics in sub-Saharan Africa: potential role of historical changes in risk behaviour and male circumcision

  1. Richard J Hayes1
  1. 1Epidemiology and Public Heath, London School of Hygiene and Tropical Medicine, London, UK
  2. 2Department of Public Health, Erasmus University Rotterdam, Rotterdam, the Netherlands
  3. 3Department of Microbiology, Institute of Tropical Medicine, Antwerp, Belgium
  1. Correspondence to Dr Kate K Orroth, Infectious Disease Epidemiology Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; kate.orroth{at}
  1. Contributors KO, RW, EF, JG, AB and RH designed the study. KO and RW designed and conducted the simulations and data analyses. RB and JDF designed and developed STDSIM. All authors contributed to the interpretation of the results and the writing of the manuscript.

  • Accepted 14 July 2011
  • Published Online First 16 September 2011


Background A key conclusion of the Four Cities Study, carried out to explore reasons for heterogeneity in the HIV epidemic between two cities in sub-Saharan Africa with relatively low prevalence (Cotonou and Yaoundé) and two with high prevalence (Kisumu and Ndola), was that differences in biological cofactors outweighed differences in sexual risk behaviours. The authors explore an alternative hypothesis, that risk behaviours were historically higher in the high-prevalence cities. They also investigate the effects of different prevalence of male circumcision on the HIV epidemics in the four cities.

Methods A transmission model was fitted to data from the Four Cities Study. Default scenarios included biological cofactor effects on HIV transmission. Counter-factual scenarios were simulated without biological cofactors, with and without higher historical sexual behaviours, and with various rates of male circumcision.

Results Simulated adult HIV prevalence in 1997 for the default scenarios was 3.1%, 7.8%, 28.9% and 27.1% in Cotonou, Yaoundé, Kisumu and Ndola, respectively, in line with data. Without biological cofactors, even implausibly high historical levels of risk behaviour in East Africa could not reproduce the observed heterogeneity in the late 1990s. Increasing the proportion of men circumcised in Ndola from 10% to 100% reduced HIV prevalence in 1997 to 7%. Decreasing the proportion circumcised in Yaoundé from 100% to 10% increased HIV prevalence to 26%.

Conclusions Differences in male circumcision rates are likely to have played a key role in the heterogeneous spread of HIV across Africa. The effect of circumcision interventions can vary depending on the epidemic setting, with a larger effect in more generalised epidemics.


  • Funding This study was supported by The Wellcome Trust (grant number 069509/Z/02/Z).

  • Competing interests None.

  • Provenance and peer review Commissioned; externally peer reviewed.