Mangiarotti Sylvain, Peyre Marisa, Huc Mireille
Centre d'Études Spatiales de la Biosphère, CNRS-UPS-CNES-IRD, Observatoire Midi-Pyrénées, 18 Avenue Édouard Belin, 31401 Toulouse, France.
UPR AGIRs, Bureau 208, Bâtiment E TA C22/E, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Campus International de Baillarguet, Montpellier Cedex 5 34398, France.
Chaos. 2016 Nov;26(11):113112. doi: 10.1063/1.4967730.
An epidemic of Ebola Virus Disease (EVD) broke out in Guinea in December 2013. It was only identified in March 2014 while it had already spread out in Liberia and Sierra Leone. The spill over of the disease became uncontrollable and the epidemic could not be stopped before 2016. The time evolution of this epidemic is revisited here with the global modeling technique which was designed to obtain the deterministic models from single time series. A generalized formulation of this technique for multivariate time series is introduced. It is applied to the epidemic of EVD in West Africa focusing on the period between March 2014 and January 2015, that is, before any detected signs of weakening. Data gathered by the World Health Organization, based on the official publications of the Ministries of Health of the three main countries involved in this epidemic, are considered in our analysis. Two observed time series are used: the daily numbers of infections and deaths. A four-dimensional model producing a very complex dynamical behavior is obtained. The model is tested in order to investigate its skills and drawbacks. Our global analysis clearly helps to distinguish three main stages during the epidemic. A characterization of the obtained attractor is also performed. In particular, the topology of the chaotic attractor is analyzed and a skeleton is obtained for its structure.
2013年12月，几内亚爆发了埃博拉病毒病疫情。直到2014年3月才确认疫情，而此时该疾病已在利比里亚和塞拉利昂蔓延开来。疾病的传播变得无法控制，疫情直到2016年才得到遏制。本文运用全局建模技术重新审视了此次疫情的时间演变，该技术旨在从单时间序列中获取确定性模型。本文介绍了这种针对多变量时间序列的技术的广义公式。将其应用于西非埃博拉病毒病疫情，重点关注2014年3月至2015年1月期间，即任何减弱迹象出现之前。我们的分析采用了世界卫生组织收集的数据，这些数据基于疫情涉及的三个主要国家卫生部的官方出版物。使用了两个观测时间序列：每日感染数和死亡数。得到了一个产生非常复杂动力学行为的四维模型。对该模型进行了测试，以研究其优缺点。我们的全局分析清楚地有助于区分疫情期间的三个主要阶段。还对得到的吸引子进行了特征描述。特别是，分析了混沌吸引子的拓扑结构，并获得了其结构的一个骨架。
