title: Concurrent partnerships in Cape Town, South Africa: race and sex differences in prevalence and duration of overlap.
abstract: BACKGROUND
  Concurrent partnerships (CPs) have been suggested as a risk factor for transmitting HIV, but their impact on the epidemic depends upon how prevalent they are in populations, the average number of CPs an individual has and the length of time they overlap. However, estimates of prevalence of CPs in Southern Africa vary widely, and the duration of overlap in these relationships is poorly documented. We aim to characterize concurrency in a more accurate and complete manner, using data from three disadvantaged communities of Cape Town, South Africa.
  
  
  METHODS
  We conducted a sexual behaviour survey (n = 878) from June 2011 to February 2012 in Cape Town, using Audio Computer-Assisted Self-Interviewing to collect sexual relationship histories on partners in the past year. Using the beginning and end dates for the partnerships, we calculated the point prevalence, the cumulative prevalence and the incidence rate of CPs, as well as the duration of overlap for relationships begun in the previous year. Linear and binomial regression models were used to quantify race (black vs. coloured) and sex differences in the duration of overlap and relative risk of having CPs in the past year.
  
  
  RESULTS
  The overall point prevalence of CPs six months before the survey was 8.4%: 13.4% for black men, 1.9% for coloured men, 7.8% black women and 5.6% for coloured women. The median duration of overlap in CPs was 7.5 weeks. Women had less risk of CPs in the previous year than men (RR 0.43; 95% CI: 0.32-0.57) and black participants were more at risk than coloured participants (RR 1.86; 95% CI: 1.17-2.97).
  
  
  CONCLUSIONS
  Our results indicate that in this population the prevalence of CPs is relatively high and is characterized by overlaps of long duration, implying there may be opportunities for HIV to be transmitted to concurrent partners.
authors.affiliation: The South African Department of Science and Technology/National Research Foundation (DST/NRF) Centre of Excellence in Epidemiological Modelling and Analysis (SACEMA), Stellenbosch University, Stellenbosch, South Africa.|International Centre for Reproductive Health, Ghent University, Gent, Belgium; roxanne.beauclair@gmail.com.
authors.forename: Roxanne
authors.initials: R
authors.lastname: Beauclair
authors.affiliation: Center for Statistics, Hasselt University, Diepenbeek, Belgium.|Centre for Health Economic Research and Modeling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Wilrijk, Belgium.
authors.forename: Niel
authors.initials: N
authors.lastname: Hens
authors.affiliation: The South African Department of Science and Technology/National Research Foundation (DST/NRF) Centre of Excellence in Epidemiological Modelling and Analysis (SACEMA), Stellenbosch University, Stellenbosch, South Africa.|International Centre for Reproductive Health, Ghent University, Gent, Belgium.|Center for Statistics, Hasselt University, Diepenbeek, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Delva
mesh_terms: D000328:Adult; D000353:Africa, Southern; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012727:Sex Characteristics; D012725:Sexual Behavior / Q000706:statistics & numerical data; D013019:South Africa / Q000453:epidemiology
keywords: HIV prevention; South Africa; concurrent partnerships; sexual behaviour and HIV; sexual concurrency; sexual risk behaviour