Odum School of Ecology, University of Georgia, Athens, GA 30602, USA.
Biology Department, Stanford University, 371 Serra Mall, Stanford, CA, USA.
Biol Lett. 2020 Mar;16(3):20190713. doi: 10.1098/rsbl.2019.0713. Epub 2020 Mar 18.
Campaigns to eliminate infectious diseases could be greatly aided by methods for providing early warning signals of resurgence. Theory predicts that as a disease transmission system undergoes a transition from stability at the disease-free equilibrium to sustained transmission, it will exhibit characteristic behaviours known as critical slowing down, referring to the speed at which fluctuations in the number of cases are dampened, for instance the extinction of a local transmission chain after infection from an imported case. These phenomena include increases in several summary statistics, including lag-1 autocorrelation, variance and the first difference of variance. Here, we report the first empirical test of this prediction during the resurgence of malaria in Kericho, Kenya. For 10 summary statistics, we measured the approach to criticality in a rolling window to quantify the size of effect and directions. Nine of the statistics increased as predicted and variance, the first difference of variance, autocovariance, lag-1 autocorrelation and decay time returned early warning signals of critical slowing down based on permutation tests. These results show that time series of disease incidence collected through ordinary surveillance activities may exhibit characteristic signatures prior to an outbreak, a phenomenon that may be quite general among infectious disease systems.
消除传染病的运动可以通过提供传染病复发预警信号的方法得到极大的帮助。理论预测，当疾病传播系统从无病平衡点的稳定状态过渡到持续传播时，它将表现出特征性行为，称为临界减速，指的是病例数量波动的速度被抑制，例如，在输入病例感染后，局部传播链的灭绝。这些现象包括几个汇总统计量的增加，包括滞后 1 自相关、方差和方差的一阶差分。在这里，我们在肯尼亚克里乔的疟疾复发期间首次对这一预测进行了实证检验。对于 10 个汇总统计量，我们在滚动窗口中测量了接近临界点的情况，以量化效应的大小和方向。正如预测的那样，有 9 项统计数据增加了，而方差、方差的一阶差分、自协方差、滞后 1 自相关和衰减时间则根据排列检验返回了临界减速的预警信号。这些结果表明，通过常规监测活动收集的疾病发病率时间序列在爆发前可能表现出特征性特征，这种现象在传染病系统中可能相当普遍。
