Awad Susanne F, Abu-Raddad Laith J
Infectious Disease Epidemiology Group, Weill Cornell Medical College - Qatar, Cornell University, Qatar Foundation - Education City, Doha, Qatar.
Infectious Disease Epidemiology Group, Weill Cornell Medical College - Qatar, Cornell University, Qatar Foundation - Education City, Doha, Qatar; Department of Healthcare Policy and Research, Weill Cornell Medical College, Cornell University, New York, NY, USA; Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
Epidemics. 2014 Sep;8:9-17. doi: 10.1016/j.epidem.2014.06.001. Epub 2014 Jul 1.
HIV prevalence is decreasing in much of sub-Saharan Africa (SSA), but the drivers of the decline are subject to much dispute. Using mathematical modeling as a tool for hypothesis generation, we demonstrate how the hypothesis that the drop in prevalence reflects declines in sexual risk behavior is self-consistent. We characterize these potential declines in terms of their scale, duration, and timing, and theorize on how small changes in sexual behavior at the individual-level could have driven large declines in HIV prevalence.
A population-level deterministic compartmental model was constructed to describe the HIV epidemics in 24 countries in SSA with sufficient trend data. The model was parameterized by national HIV prevalence and HIV natural history and transmission data. The temporal evolution of sexual risk behavior was characterized using established tools and uncertainty and sensitivity analyses on the results were conducted.
Declines in the scale of sexual risk behavior between 31.8% (Botswana) and 89.3% (Liberia) can explain the declining HIV prevalence across countries. The average decline across countries was 68.9%. The transition in sexual risk behavior lasted between 2.7 (Botswana) and 16.6 (Gabon) years with an average of 8.2 years. The turning point year of the transition occurred between 1993 (Burundi) and 2001 (Namibia), but clustered around 1995 for most countries. The uncertainty and sensitivity analyses affirmed our model predictions.
The hypothesis that HIV prevalence declines in SSA have been driven by declines in sexual risk behavior is self-consistent and provides a convincing narrative for an evolving HIV epidemiology in this region. The hypothesized declines must have been remarkable in their intensity, rapidity, and synchronicity to explain the temporal trends in HIV prevalence. These findings provide contextual support for the hypothesis that changes in sexual behavior that materialized in the 1990s are a dominant driver of the recent decreases in HIV prevalence.
撒哈拉以南非洲（SSA）大部分地区的艾滋病毒流行率正在下降，但下降的驱动因素存在诸多争议。我们使用数学建模作为假设生成工具，证明了流行率下降反映性风险行为下降这一假设是自洽的。我们从规模、持续时间和时间点方面描述了这些潜在的下降情况，并对个体层面性行为的微小变化如何导致艾滋病毒流行率大幅下降进行了理论分析。
构建了一个人群水平的确定性 compartmental 模型，以描述具有足够趋势数据的 SSA 24 个国家的艾滋病毒流行情况。该模型通过国家艾滋病毒流行率以及艾滋病毒自然史和传播数据进行参数化。使用既定工具对性风险行为的时间演变进行了描述，并对结果进行了不确定性和敏感性分析。
性风险行为规模下降幅度在 31.8%（博茨瓦纳）至 89.3%（利比里亚）之间，可以解释各国艾滋病毒流行率的下降情况。各国的平均下降幅度为 68.9%。性风险行为的转变持续了 2.7 年（博茨瓦纳）至 16.6 年（加蓬），平均为 8.2 年。转变的转折点年份在 1993 年（布隆迪）至 2001 年（纳米比亚）之间，但大多数国家集中在 1995 年左右。不确定性和敏感性分析证实了我们的模型预测。
SSA 地区艾滋病毒流行率下降是由性风险行为下降所驱动这一假设是自洽的，并为该地区不断演变的艾滋病毒流行病学提供了一个有说服力的解释。假设的下降情况在强度、速度和同步性方面必定非常显著，才能解释艾滋病毒流行率的时间趋势。这些发现为 20 世纪 90 年代出现的性行为变化是近期艾滋病毒流行率下降的主要驱动因素这一假设提供了背景支持。
