Extra-couple HIV transmission in sub-Saharan Africa: a mathematical modelling study of survey data

Abstract

Summary Background The proportion of heterosexual HIV transmission in Sub-Saharan Africa that occurs within cohabiting partnerships, as opposed to among single people, or in extra-couple relationships, is a subject of active debate. This question is of immediate importance. As plans to use antiretroviral drugs as a strategy for population-level prevention progress, understanding the importance of different transmission routes is critical to targeting intervention efforts. Methods We built a mechanistic HIV transmission model using data from Demographic and Health Surveys covering 27,201 cohabiting couples from 18 sub-Saharan African countries with information on couple duration, age at sexual debut, and HIV serostatus. We combined this model with estimates of HIV survival times and country-specific estimates of HIV prevalence and ART coverage. We then estimated the proportion of observed infections in surveyed cohabiting couples that occurred prior to couple formation, between couple members, and through extra-couple intercourse. Findings We estimate that extra-couple transmission accounts for between 27-61% and 21-51% of all infected males and females, respectively, in surveyed couples, with the ranges given reflecting inter-country variation. We project that over the next year extra-couple transmission will account for 30-65% and 10-47% of new incident HIV infections in males and females, respectively, in cohabiting couples. Our results also suggest that the directionality of transmission within couples is largely from males to females; however, females experience a very high-risk period prior to couple formation. Interpretation Due to the large contribution of extra-couple transmission, HIV prevention interventions should target the general sexually active population, and not just serodiscordant couples.

Advances in HIV Prevention for Serodiscordant Couples

“…Up to 27% of transmission events in the HPTN052 and Partners Study were attributable to external events [19, 67]. In a recent modeling study of extra-couple HIV transmission in sub-Saharan Africa, researchers estimated that 27 to 61% of all HIV infections among men and 21 to 51% of infections among women were attributable to extra-couple events [68]. Second, couples may not want to start ART early.…”

Effectiveness of combination packages for HIV-1 prevention in sub-Saharan Africa depends on partnership network structure: a mathematical modelling study

“…This is largely possible by allowing for concurrency: unlike most compartmental models, we can model HIV transmission potential within a heterosexual couple that starts as concordant-negative, then becomes discordant because of an outside partnership, then becomes concordant-positive. 26 Our stochastic methods also improve on the predominant deterministic modelling methods by providing a range of plausible outcomes associated with each scenario, including the predicted extinction probability.…”

The Impact of Married Individuals Learning HIV Status in Malawi: Divorce, Number of Sexual Partners, and Condom Use With Spouses

“…Several studies have indicated that a moderate to large proportion of new heterosexually acquired HIV infections occur within marriage or stable relationships (Bellan et al 2013; Chemaitelly et al 2014; Dunkle et al 2008; Matovu 2010; UNAIDS 2010), and serodiscordant couples are more common than seroconcordant HIV-positive couples (De Walque 2007). Serodiscordant couples can arise from extramarital partnerships but also from premarital partners and prior marriages.…”