HIV expansion is controlled by a range of interrelated factors, including the natural history of HIV infection and socio-economical and structural factors. However, how they dynamically interact in particular contexts to drive a transition from concentrated HIV epidemics in vulnerable groups to generalized epidemics is poorly understood. We aim to explore these mechanisms, using Madagascar as a case-study. 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. The model predicts sigmoidal-like prevalence curves with turning points within years 2020–2022, and prevalence reaching stabilization by 2033 within 9 to 24% in the studied (10 out of 11) cities, similar to high-prevalence regions in Southern Africa. The late/slow introduction of HIV and circumcision, a widespread traditional practice in Madagascar, could have slowed down HIV propagation, but, given the key interplay between risky behaviors associated to young women 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. These results suggest that Madagascar may be experiencing a silent transition from a concentrated to a generalized HIV epidemic. This case-study model could help to understand how this HIV epidemic transition occurs.

中文翻译：

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艾滋病毒流行从集中流行到普遍流行的潜在转变：马达加斯加的案例

HIV 的传播受到一系列相互关联的因素的控制，包括 HIV 感染的自然史以及社会经济和结构因素。然而，人们对它们如何在特定环境下动态相互作用以推动从弱势群体集中的艾滋病毒流行向普遍流行的转变仍知之甚少。我们的目标是以马达加斯加为案例研究来探索这些机制。我们利用马达加斯加（一个疫情较为集中的国家）的现有数据开发了一个区室动态模型，以探索这些因素之间的相互作用，并特别考虑商业和交易性行为作为艾滋病毒感染的驱动因素。该模型预测 S 形患病率曲线，在 2020 年至 2022 年之间出现转折点，到 2033 年，研究城市（11 个城市中的 10 个）患病率将稳定在 9% 至 24% 之间，与南部非洲的高患病率地区类似。艾滋病毒的较晚/缓慢引入和包皮环切术是马达加斯加普遍存在的传统做法，本可以减缓艾滋病毒的传播，但是，考虑到与年轻女性相关的危险行为和由性交易介导的急性感染流行之间的关键相互作用，保护作用目前包皮环切术不足以遏制该疾病在马达加斯加的蔓延。这些结果表明，马达加斯加可能正在经历从艾滋病毒集中流行到普遍流行的悄然转变。这个案例研究模型可以帮助理解这种艾滋病毒流行转变是如何发生的。