Leung Ka Yin, Kretzschmar Mirjam
aMathematical Institute, Utrecht University bJulius Center for Primary Care and Health Sciences, University Medical Center Utrecht cCenter for Infectious Disease Control, National Institute for Public Health and the Environment, Utrecht, The Netherlands.
AIDS. 2015 Jun 1;29(9):1097-103. doi: 10.1097/QAD.0000000000000676.
The objective of this study is to investigate whether concurrency can drive an HIV epidemic by moving R0 across the epidemic threshold.
We use a mathematical framework for a dynamic partnership network and the spread of a one-stage infection to study how concurrency is related to the basic reproduction number R0. Two concurrency indices were used to measure the level of concurrency. The model allows varying the level of concurrency in the population, while other key network properties such as partnership duration and lifetime number of partners are kept fixed. In this way, the effect of concurrency on R0 is investigated as an isolated phenomenon.
We find that an increase in concurrency is associated with an increase of R0. For plausible parameter sets for MSM populations, R0 is always above the epidemic threshold of 1. For scenarios that are plausible for sub-Saharan African populations, we show that increasing the level of concurrency can lead to R0 crossing the epidemic threshold. This occurs already at low levels of concurrency. Only a slight shift of the network structure from a purely monogamous population to one wherein individuals are allowed to have at most two partners is enough for this to happen.
Concurrency can be a driver of an HIV epidemic in sub-Saharan Africa for low levels of concurrency, although it is not decisive in MSM populations. A small increase in the level of concurrency can lead to R0 crossing the epidemic threshold in a sub-Saharan African setting.
本研究的目的是调查并发情况是否会通过使基本再生数R0超过流行阈值来推动艾滋病毒的流行。
我们使用一个动态性伙伴关系网络和单阶段感染传播的数学框架，来研究并发情况与基本再生数R0之间的关系。使用两个并发指数来衡量并发水平。该模型允许改变人群中的并发水平，同时保持伙伴关系持续时间和终身性伙伴数量等其他关键网络属性不变。通过这种方式，将并发对R0的影响作为一个孤立现象进行研究。
我们发现并发情况的增加与R0的增加相关。对于男男性行为人群合理的参数集，R0始终高于流行阈值1。对于撒哈拉以南非洲人群合理的情景，我们表明增加并发水平会导致R0超过流行阈值。这种情况在低并发水平时就会出现。网络结构仅从纯一夫一妻制人群略有转变为允许个体最多有两个性伙伴的人群，就足以发生这种情况。
在撒哈拉以南非洲，低并发水平时并发情况可能是艾滋病毒流行的一个驱动因素，尽管在男男性行为人群中并非决定性因素。并发水平的小幅增加会导致在撒哈拉以南非洲背景下R0超过流行阈值。
