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Multiple sexual partnerships must necessarily lie at the root of a sexually transmitted epidemic. However, that overlapping or concurrent partnerships have played a pivotal role in the generalized epidemics of sub‐Saharan Africa has been challenged. Much of the original proposition that concurrent partnerships play such a role focused on modelling, self‐reported sexual behaviour data and ethnographic data. While each of these has definite merit, each also has had methodological limitations. Actually, more recent cross‐national sexual behaviour data and improved modelling have strengthened these lines of evidence. However, heretofore the epidemiologic evidence has not been systematically brought to bear. Though assessing the epidemiologic evidence regarding concurrency has its challenges, a careful examination, especially of those studies that have assessed HIV incidence, clearly indicates a key role for concurrency. Such evidence includes: 1) the early and dramatic rise of HIV infection in generalized epidemics that can only arise from transmission through rapid sequential acute infections and thereby concurrency; 2) clear evidence from incidence studies that a major portion of transmission in the population occurs via concurrency both for concordant negative and discordant couples; 3) elevation in risk associated with partner's multiple partnering; 4) declines in HIV associated with declines in concurrency; 5) bursts and clustering of incident infections that indicate concurrency and acute infection play a key role in the propagation of epidemics; and 6) a lack of other plausible explanations, including serial monogamy and non‐sexual transmission. While other factors, such as sexually transmitted infections, other infectious diseases, biological factors and HIV sub‐type, likely play a role in enhancing transmission, it appears most plausible that these would amplify the role of concurrency rather than alter it. Additionally, critics of concurrency have not proposed plausible alternative explanations for why the explosive generalized epidemics occurred. Specific behaviour change messaging bringing the concepts of multiple partnering and concurrency together appears salient and valid in promoting safer individual behaviour and positive social norms., Introduction Why did generalized HIV epidemics burst upon the scene and persist at high levels only in some 14 countries in eastern and southern Africa? Just as the biology of [...]

Introduction: The recent availability of efficacious prevention interventions among stable couples offers new opportunities for reducing HIV incidence in sub‐Saharan Africa. Understanding the dynamics of HIV incidence among stable couples is critical to inform HIV prevention strategy across sub‐Saharan Africa. Methods: We quantified the sources of HIV incidence arising among stable couples in sub‐Saharan Africa using a cohort‐type mathematical model parameterized by nationally representative data. Uncertainty and sensitivity analyses were incorporated. Results: HIV incidence arising among stable concordant HIV‐negative couples contribute each year, on average, 29.4% of total HIV incidence; of those, 22.5% (range: 11.1%–39.8%) are infections acquired by one of the partners from sources external to the couple, less than 1% are infections acquired by both partners from external sources within a year and 6.8% (range: 3.6%–11.6%) are transmissions to the uninfected partner in the couple in less than a year after the other partner acquired the infection from an external source. The mean contribution of stable HIV sero‐discordant couples to total HIV incidence is 30.4%, with most of those, 29.7% (range: 9.1%–47.9%), being due to HIV transmissions from the infected to the uninfected partner within the couple. The remaining incidence, 40.2% (range: 23.7%–64.6%), occurs among persons not in stable couples. Conclusions: Close to two‐thirds of total HIV incidence in sub‐Saharan Africa occur among stable couples; however, only half of this incidence is attributed to HIV transmissions from the infected to the uninfected partner in the couple. The remaining incidence is acquired through extra‐partner sex. Substantial reductions in HIV incidence can be achieved only through a prevention approach that targets all modes of HIV exposure among stable couples and among individuals not in stable couples., Introduction The majority of the adult population in sub‐Saharan Africa (SSA) live in marital or co‐habiting couples [1]. A considerable fraction of these stable couples (SCs) are HIV sero‐discordant (that [...]