Can Human Movements Explain Heterogeneous Propagation of Dengue Fever in Cambodia?

BackgroundDetermining the factors underlying the long-range spatial spread of infectious diseases is a key issue regarding their control. Dengue is the most important arboviral disease worldwide and a major public health problem in tropical areas. However the determinants shaping its dynamics at a national scale remain poorly understood. Here we describe the spatial-temporal pattern of propagation of annual epidemics in Cambodia and discuss the role that human movements play in the observed pattern. Methods and FindingsWe used wavelet phase analysis to analyse time-series data of 105,598 hospitalized cases reported between 2002 and 2008 in the 135 (/180) most populous districts in Cambodia. We reveal spatial heterogeneity in the propagation of the annual epidemic. Each year, epidemics are highly synchronous over a large geographic area along the busiest national road of the country whereas travelling waves emanate from a few rural areas and move slowly along the Mekong River at a speed of ∼11 km per week (95% confidence interval 3–18 km per week) towards the capital, Phnom Penh. ConclusionsWe suggest human movements – using roads as a surrogate – play a major role in the spread of dengue fever at a national scale. These findings constitute a new starting point in the understanding of the processes driving dengue spread.【背景】明确影响传染病长距离空间传播的关键因素，是传染病防控的核心议题。登革热（Dengue）是全球范围内最为重要的虫媒病毒性疾病，同时也是热带地区的重大公共卫生问题。然而，目前学界对塑造其国家级尺度流行动态的决定因素仍知之甚少。本研究旨在阐明柬埔寨年度登革热疫情传播的时空模式，并探讨人类移动在该观测模式中所扮演的角色。 【方法与结果】本研究采用小波相位分析（wavelet phase analysis），对柬埔寨135个（共180个）人口最多的区县在2002年至2008年间报告的105598例住院病例的时间序列数据进行分析。研究揭示了年度登革热疫情传播的空间异质性：每年，沿该国最繁忙国道的大片区域内，疫情呈现高度同步性；而少数农村地区则会产生传播波，沿湄公河以约11公里/周（95%置信区间：3~18公里/周）的速度缓慢向首都金边（Phnom Penh）移动。 【结论】本研究提示，以道路作为替代指标的人类移动，在登革热的国家级尺度传播中发挥着核心作用。本研究结果为理解驱动登革热传播的相关过程提供了全新的研究起点。