{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T05:49:17Z","timestamp":1790920157217,"version":"4.1.0"},"reference-count":29,"publisher":"BMJ","issue":"7","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sex Transm Infect"],"accepted":{"date-parts":[[2011,7,14]]},"published-print":{"date-parts":[[2011,12]]},"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>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 Yaound\u00e9) 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.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>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.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Simulated adult HIV prevalence in 1997 for the default scenarios was 3.1%, 7.8%, 28.9% and 27.1% in Cotonou, Yaound\u00e9, 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 Yaound\u00e9 from 100% to 10% increased HIV prevalence to 26%.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>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.<\/jats:p><\/jats:sec>","DOI":"10.1136\/sextrans-2011-050174","type":"journal-article","created":{"date-parts":[[2011,9,17]],"date-time":"2011-09-17T02:31:12Z","timestamp":1316226672000},"page":"640-645","source":"Crossref","is-referenced-by-count":8,"title":["Attempting to explain heterogeneous HIV epidemics in sub-Saharan Africa: potential role of historical changes in risk behaviour and male circumcision"],"prefix":"10.1136","volume":"87","author":[{"given":"Kate K","family":"Orroth","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard G","family":"White","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Esther E","family":"Freeman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roel","family":"Bakker","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne","family":"Buv\u00e9","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Judith R","family":"Glynn","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J Dik F","family":"Habbema","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard J","family":"Hayes","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2011,9,16]]},"reference":[{"issue":"Suppl 4","key":"2024051320484899000_87.7.640.1","doi-asserted-by":"crossref","first-page":"S5","DOI":"10.1097\/00002030-200108004-00002","article-title":"Multicentre study on factors determining differences in rate of spread of HIV in sub-Saharan Africa: methods and prevalence of HIV infection","volume":"15","author":"Buv\u00e9","year":"2001","journal-title":"AIDS"},{"issue":"Suppl 4)","key":"2024051320484899000_87.7.640.2","doi-asserted-by":"crossref","first-page":"S31","DOI":"10.1097\/00002030-200108004-00004","article-title":"Male circumcision and HIV infection in four cities in sub-Saharan Africa","volume":"15","author":"Auvert","year":"2001","journal-title":"AIDS"},{"key":"2024051320484899000_87.7.640.3","doi-asserted-by":"publisher","DOI":"10.1097\/00002030-200108004-00011"},{"issue":"Suppl 4)","key":"2024051320484899000_87.7.640.4","doi-asserted-by":"crossref","first-page":"S41","DOI":"10.1097\/00002030-200108004-00005","article-title":"Comparison of key parameters of sexual behaviour in four African urban populations with different levels of HIV infection","volume":"15","author":"Ferry","year":"2001","journal-title":"AIDS"},{"issue":"Suppl 4)","key":"2024051320484899000_87.7.640.5","doi-asserted-by":"crossref","first-page":"S61","DOI":"10.1097\/00002030-200108004-00007","article-title":"Commercial sex and the spread of HIV in four cities in sub-Saharan Africa","volume":"15","author":"Morison","year":"2001","journal-title":"AIDS"},{"key":"2024051320484899000_87.7.640.6","doi-asserted-by":"publisher","DOI":"10.1136\/sti.2006.023531"},{"key":"2024051320484899000_87.7.640.7","doi-asserted-by":"publisher","DOI":"10.1097\/00007435-200111000-00001"},{"key":"2024051320484899000_87.7.640.8","first-page":"1","article-title":"The cofactor effect of genital ulcers on the per-exposure risk of HIV transmission in sub-Saharan Africa","volume":"98","author":"Hayes","year":"1995","journal-title":"J Trop Med Hyg"},{"key":"2024051320484899000_87.7.640.9","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pmed.0020298"},{"key":"2024051320484899000_87.7.640.10","doi-asserted-by":"publisher","DOI":"10.1097\/00002030-200010200-00018"},{"key":"2024051320484899000_87.7.640.11","doi-asserted-by":"publisher","DOI":"10.1136\/sti.2005.017442"},{"key":"2024051320484899000_87.7.640.12","doi-asserted-by":"publisher","DOI":"10.1016\/j.epidem.2009.08.001"},{"key":"2024051320484899000_87.7.640.13","doi-asserted-by":"publisher","DOI":"10.1080\/08898480009525479"},{"key":"2024051320484899000_87.7.640.14","unstructured":"van Vliet C Holmes KK Singer B . 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