|Extra-couple HIV transmission in sub-Saharan Africa: A mathematical modelling study of survey data|
||Steve E Bellan, Kathryn J Fiorella, Dessalegn Y Melesse, Wayne M Getz, Brian G Williams, Jonathan Dushoff
||Lancet, Volume 381, Issue 9877, Pages 1561 - 1569, doi:10.1016/S0140-6736(12)61960-6
Multiple African Countries
||Background The proportion of heterosexual HIV transmission in sub-Saharan Africa that occurs within cohabiting
partnerships, compared with that in single people or extra-couple relationships, is widely debated. We estimated the
proportional contribution of diff erent routes of transmission to new HIV infections. As plans to use antiretroviral
drugs as a strategy for population-level prevention progress, understanding the importance of diff erent transmission
routes is crucial to target intervention eff orts.
Methods We built a mechanistic model of HIV transmission with data from Demographic and Health Surveys
(DHS) for 2003–2011, of 27 201 cohabiting couples (men aged 15–59 years and women aged 15–49 years) from
18 sub-Saharan African countries with information about relationship duration, age at sexual debut, and HIV
serostatus. We combined this model with estimates of HIV survival times and country-specifi c estimates of HIV
prevalence and coverage of antiretroviral therapy (ART). We then estimated the proportion of recorded infections in
surveyed cohabiting couples that occurred before couple formation, between couple members, and because of extracouple
Findings In surveyed couples, we estimated that extra-couple transmission accounted for 27–61% of all HIV infections
in men and 21–51% of all those in women, with ranges showing intercountry variation. We estimated that in 2011,
extra-couple transmission accounted for 32–65% of new incident HIV infections in men in cohabiting couples, and
10–47% of new infections in women in such couples. Our fi ndings suggest that transmission within couples occurs
largely from men to women; however, the latter sex have a very high-risk period before couple formation.
Interpretation Because of the large contribution of extra-couple transmission to new HIV infections, interventions for
HIV prevention should target the general sexually active population and not only serodiscordant couples.