Di Lauro Francesco, Probert William J M, Pickles Michael, Cori Anne, Hinch Robert, Ferretti Luca, Panovska-Griffiths Jasmina, Abeler-Dörner Lucie, Dunbar Rory, Bock Peter, Donnell Deborah J, Ayles Helen, Fidler Sarah, Hayes Richard, Fraser Christophe
Pandemic Sciences Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom.
School of Public Health, Imperial College, London, United Kingdom.
J Theor Biol. 2025 Oct 7;613:112218. doi: 10.1016/j.jtbi.2025.112218. Epub 2025 Jul 16.
The HIV epidemic in sub-Saharan Africa is historically characterised by high levels of prevalence and incidence. With the global effort to reach UNAIDS 95-95-95 targets, the scaling-up of HIV treatment, and focused preventive interventions, incidence has been declining over the past decade, albeit non-consistently across different sex and age groups. Two questions remain to be addressed to help tailor setting-specific interventions and allocate resources optimally. Firstly, are there unidentified demographic groups that are sources of transmission? Secondly, what are the patterns of decline in incidence across different groups? Model-based assessment is a valuable tool for the design of focused interventions and to answer these questions. PopART-IBM, an individual-based model calibrated to (anonymised) age-and-sex stratified data, was developed in the context of the HPTN-071 (PopART) trial, and it offers a unique opportunity to explore such questions in the context of high-burden HIV communities in Zambia and South Africa. The outputs of the model include the full HIV transmission and partnership networks. In this work, we explore these and show that the sexual partnership network exhibits a large connected component, usually comprising over 40 % of the population, in each of the studied communities. An analysis of the large connected component reveals that it is formed by young people (20-40 years old) and is centered around the most sexually active individuals of the community. At the same time, many individuals in the large connected component only have one partner, highlighting the complex dynamics of risk correlations in a population. Inspecting the transmission network reveals that, on average, more than 80% of transmissions occur among individuals belonging to the large connected component. These findings indicate that populations consisting of young and highly sexually active individuals should be given high priority when designing or deploying interventions.
撒哈拉以南非洲的艾滋病疫情历来具有高流行率和高发病率的特点。随着全球为实现联合国艾滋病规划署的95-95-95目标、扩大艾滋病治疗规模以及开展重点预防干预措施，发病率在过去十年中一直在下降，尽管不同性别和年龄组的下降情况并不一致。为了帮助制定针对特定环境的干预措施并优化资源分配，仍有两个问题有待解决。首先，是否存在未被识别的传播人群？其次，不同群体发病率下降的模式是怎样的？基于模型的评估是设计重点干预措施和回答这些问题的宝贵工具。PopART-IBM是一种基于个体的模型，已根据（匿名的）年龄和性别分层数据进行校准，它是在HPTN-071（PopART）试验的背景下开发的，为在赞比亚和南非高负担艾滋病社区的背景下探索此类问题提供了独特机会。该模型的输出包括完整的艾滋病传播和性伴侣网络。在这项工作中，我们对这些进行了探索，并表明性伴侣网络在每个研究社区中都呈现出一个大型连通组件，通常占人口的40%以上。对这个大型连通组件的分析表明，它由年轻人（20至40岁）组成，并且以社区中最活跃的性活跃个体为中心。与此同时，大型连通组件中的许多个体只有一个伴侣，这凸显了人群中风险关联的复杂动态。检查传播网络发现，平均而言，超过80%的传播发生在属于大型连通组件的个体之间。这些发现表明，在设计或部署干预措施时，应高度优先考虑由年轻且性活跃的个体组成的人群。
