LB 13-127 - A potential transition from a concentrated to a generalized HIV epidemic: the case of Madagascar

HIV expansion is controlled by a range of interrelated factors, including the natural history of HIV infection, population demography (mobility and population density), cultural and social values (i.e. circumcision and women social vulnerability), legal framework and human rights respect, economic disruptions, and geopolitics. However, how they dynamically interact in particular contexts to drive a transition from concentrated HIV epidemics (when the infection occurs largely in defined vulnerable groups) to generalized epidemics (when transmission is sustained within the general population with prevalence over 1%) is poorly understood. Here, we developed a compartmental dynamic model using available data from Madagascar, a country with a contrasting concentrated epidemic, to explore the interaction between these factors with special consideration of commercial and transactional sex as HIV-infection drivers. We predict sigmoidal-like prevalence curves with turning points within years 2020-2022, and prevalence reaching stabilization by 2033 within 9 to 24% in the (10 out of 11) studied cities, similar to high-prevalence regions in Southern Africa. Circumcision could have slowed down HIV propagation, but, given the key interplay between risky behaviors associated to young women (i.e. age disparate-concurrency) and acute infections prevalence, mediated by transactional sex, the protective effect of circumcision is currently insufficient to contain the expansion of the disease in Madagascar. Our results suggest that Madagascar may be experiencing a silent transition from a concentrated to a generalized HIVepidemic. Pandemics, such as Covid19, may contribute to accelerate this transition in an economic frail country such as Madagascar. Our work should raise alarm bells before the transition we foresee here occurs, and help to implement targeted strategies to avoid it, not only in Madagascar, but in other regions as well.