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Objectives Much of our understanding about the effect of concurrent sexual partnerships on the spread of HIV derives from mathematical models, but the empirical evidence is limited. In this contribution, we focus on polygyny, a common and institutionalized form of concurrency for which data are available, and study its relationship with HIV prevalence at the ecological level. Methods First, we describe country-level variation in the prevalence of polygyny and HIV. Second, we test the relationship between HIV and polygyny at the sub-national level using country fixed-effects regression models with data from nineteen Demographic and Health Surveys. Results The ecological association between polygyny and HIV prevalence is negative at the country as well as sub-national level: HIV prevalence is lower in countries where the practice of polygyny is common, and within countries it is lower in areas with higher levels of polygyny. Proposed explanations for the protective effect of polygyny include the distinctive structure of sexual networks produced by polygyny, the disproportionate recruitment of HIV positive women into marriages with a polygynous husband, and the lower coital frequency in conjugal dyads of polygynous marriages. Conclusion Existing mathematical models of concurrency are not sufficiently specific to account for the relatively benign effect of polygyny on the spread of HIV, and require refinements before they are used to inform HIV prevention policies.

Objectives Assessments of population-level effects of antiretroviral therapy (ART) programs in Africa are rare. We use data from burial sites to estimate trends in adult AIDS mortality and the mitigating effects of ART in Addis Ababa. ART has been available since 2003, and for free since 2005. Methods To substitute for deficient vital registration, we use surveillance of burials at all cemeteries. We present trends in all-cause mortality, and estimate AIDS mortality (ages 20–64) from lay reports of causes of death. These lay reports are first used as a diagnostic test for the true cause of death. As reference standard we use the cause of death established via verbal autopsy interviews conducted in 2004. The Positive Predictive Value and Sensitivity are subsequently used as anchors to estimate the number of AIDS deaths for the period 2001–2007. Estimates are compared with Spectrum projections. Results Between 2001 and 2005, the number of AIDS deaths declined by 21.9% and 9.3% for men and women, respectively. Between 2005 and 2007, the number of AIDS deaths declined by 38.2% for men and 42.9% for women. Compared to the expected number in the absence of ART, the reduction in AIDS deaths in 2007 is estimated between 56.8% and 63.3%, depending on the coverage of the burial surveillance. Conclusion Five years into the ART program, adult AIDS mortality has been reduced by more than half. Following the free provision of ART in 2005, the decline accelerated and became more gender balanced. Substantial AIDS mortality, however, persists.