The importance of concurrency (overlapping sexual partnerships in which sexual intercourse with one partner occurs between two acts of intercourse with another partner) in driving HIV transmission in hyperendemic settings remains controversial. A modelling study concluded that the role of concurrency in accelerating the spread of HIV is dramatically reduced by coital dilution (the reduction in frequency of sex acts per sexual partner, as a result of acquiring additional partners). We recently examined self-reported data on coital frequency and condom use during monogamous and concurrent relationship episodes from a survey in three communities with a high HIV prevalence. A key question in our analysis was if there is evidence for coital dilution and/or increased condom use during episodes of concurrency.
In Swaziland the risk of getting HIV infected is significantly higher among young women compared to young men. These differences cannot be explained by anatomical and hormonal factors that make young women particularly vulnerable to HIV infection. In this article the results of a secondary analysis of the Swaziland Demographic and Health Survey 2006-2007 data is described. In particular, trends and variability in age differences between young men and their female sexual partners are explored. In addition the magnitude of the age difference between sexual partners and the association with consistent condom use is examined.