State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
PLoS Negl Trop Dis. 2013 Sep 19;7(9):e2459. doi: 10.1371/journal.pntd.0002459. eCollection 2013.
Although a previous study predicted that Japanese encephalitis virus (JEV) originated in the Malaysia/Indonesia region, the virus is known to circulate mainly on the Asian continent. However, there are no reported systematic studies that adequately define how JEV then dispersed throughout Asia.
METHODOLOGY/PRINCIPAL FINDINGS: In order to understand the mode of JEV dispersal throughout the entire Asian continent and the factors that determine the dispersal characteristics of JEV, a phylogenetic analysis using Bayesian Markov chain Monte Carlo simulations was conducted on all available JEV E gene sequences in GenBank, plus strains recently isolated in China. Here we demonstrate for the first time that JEV lineages can be divided into four endemic cycles, comprising southern Asia, eastern coastal Asia, western Asia, and central Asia. The isolation places of the viruses in each endemic cycle were geographically independent regardless of years, vectors, and hosts of isolation. Following further analysis, we propose that the southernmost region (Thailand, Vietnam, and Yunnan Province, China) was the source of JEV transmission to the Asian continent following its emergence. Three independent transmission routes from the south to north appear to define subsequent dispersal of JEV. Analysis of JEV population dynamics further supports these concepts.
CONCLUSIONS/SIGNIFICANCE: These results and their interpretation provide new insights into our understanding of JEV evolution and dispersal and highlight its potential for introduction into non-endemic areas.
尽管先前的一项研究预测日本脑炎病毒（JEV）起源于马来西亚/印度尼西亚地区，但该病毒主要在亚洲大陆传播。然而，目前尚无报道系统的研究充分定义 JEV 是如何在亚洲传播的。
方法/主要发现：为了了解 JEV 在整个亚洲大陆的传播方式以及决定 JEV 传播特征的因素，我们使用贝叶斯马尔可夫链蒙特卡罗模拟对 GenBank 中所有可用的 JEV E 基因序列进行了系统发育分析，并加上了最近在中国分离的毒株。在这里，我们首次证明 JEV 株系可以分为四个地方性循环，包括南亚、东亚沿海、西亚和中亚。每个地方性循环中病毒的分离地点在地理位置上是相互独立的，与分离年份、媒介和宿主无关。进一步分析后，我们提出 JEV 传播到亚洲大陆的源头是最南端的地区（泰国、越南和中国云南省）。从南到北的三条独立的传播途径似乎定义了 JEV 随后的扩散。对 JEV 种群动态的分析进一步支持了这些概念。
结论/意义：这些结果及其解释为我们理解 JEV 的进化和传播提供了新的视角，并强调了它在引入非地方性地区的潜力。
