Agent-Based Modelling Laboratory, York University, Toronto, Canada.
Departamento de Física, Instituto de Ciências Exatas - ICEx, Universidade Federal Fluminense, Volta Redonda, RJ, Brazil.
Sci Rep. 2017 Jul 19;7(1):5829. doi: 10.1038/s41598-017-05013-9.
Following the 2013-14 outbreak in French Polynesia, the Zika virus (ZIKV) epidemic spread widely to many countries where Aedes Aegypti as the main transmitting vector is endemic. The lack of a second wave of ZIKV infection in most affected regions may suggest that a sufficiently high level of herd immunity was reached during the first wave. We developed an agent-based transmission model to investigate the role of asymptomatic infection on the likelihood of observing a second wave, while accounting for its relative transmissibility. We found that, as the relative transmissibility of asymptomatic infection increases, a second wave is more likely to occur, despite an increase in the attack rate during the first wave. When the reproduction number varies between 1.9 and 2.8 based on estimates for Antioquia, Colombia, the attack rate varies between 4% and 26% for a low (below 10%) effectiveness of interventions in blunting the ZIKV transmission from symptomatic cases to mosquitoes. Moreover, the fraction of cases due to sexual transmission is estimated below 4% of the cumulative incidence. Our analyses underscore the need to quantify the transmissibility of asymptomatic infections, without which the overall attack rates and the level of herd immunity cannot be accurately estimated.
继 2013-14 年法属波利尼西亚暴发疫情之后，寨卡病毒（ZIKV）广泛传播至许多埃及伊蚊为主要传播媒介的地方性流行地区。大多数受影响地区未出现寨卡病毒第二次感染浪潮，这可能表明在第一次感染浪潮中达到了足够高的群体免疫力水平。我们开发了一种基于代理的传播模型，以研究无症状感染在观察第二次感染浪潮中的作用，同时考虑到其相对传染性。我们发现，随着无症状感染的相对传染性增加，即使在第一次感染浪潮中发病率增加，也更有可能出现第二次感染浪潮。当根据哥伦比亚安蒂奥基亚省的估计，繁殖数在 1.9 到 2.8 之间变化时，在降低寨卡病毒从有症状病例向蚊子传播的干预措施效果较低（低于 10%）的情况下，发病率在 4%到 26%之间变化。此外，性传播病例的比例估计低于累积发病率的 4%。我们的分析强调了量化无症状感染传染性的必要性，否则无法准确估计总发病率和群体免疫力水平。
