Han Na, Adams James, Fang Wei, Liu Si-Qing, Rayner Simon
State Key Laboratory for Infectious Diseases Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China.
Virol Sin. 2015 Aug;30(4):277-89. doi: 10.1007/s12250-015-3621-4. Epub 2015 Aug 18.
Japanese encephalitis is a mosquito borne disease and is the leading cause of viral encephalitis in the Asia-Pacific area. The causative agent, Japanese encephalitis virus (JEV) can be phylogenetically classified into five genotypes based on nucleotide sequence. In recent years, genotype I (GI) has displaced genotype III (GIII) as the dominant lineage, but the mechanisms behind this displacement event requires elucidation. In an earlier study, we compared host variation over time between the two genotypes and observed that GI appears to have evolved to achieve more efficient infection in hosts in the replication cycle, with the tradeoff of reduced infectivity in secondary hosts such as humans. To further investigate this phenomenon, we collected JEV surveillance data on human cases and, together with sequence data, and generated genotype/case profiles from seven Asia-Pacific countries and regions to characterize the GI/GIII displacement event. We found that, when comprehensive and consistent vaccination and surveillance data was available, and the GIII to GI shift occurred within a well-defined time period, there was a statistically significant drop in JEV human cases. Our findings provide further support for the argument that GI is less effective in infecting humans, who represent a dead end host. However, experimental investigation is necessary to confirm this hypothesis. The study highlights the value of alternative approaches to investigation of epidemics, as well as the importance of effective data collection for disease surveillance and control.
日本脑炎是一种由蚊子传播的疾病，是亚太地区病毒性脑炎的主要病因。病原体日本脑炎病毒（JEV）根据核苷酸序列在系统发育上可分为五种基因型。近年来，基因型I（GI）已取代基因型III（GIII）成为主要谱系，但这种取代事件背后的机制需要阐明。在早期的一项研究中，我们比较了两种基因型随时间的宿主变异情况，观察到GI似乎已经进化，以便在复制周期内在宿主中实现更有效的感染，但以降低在人类等次要宿主中的感染性为代价。为了进一步研究这一现象，我们收集了关于人类病例的日本脑炎病毒监测数据，并结合序列数据，生成了来自七个亚太国家和地区的基因型/病例概况，以描述GI/GIII取代事件。我们发现，当有全面且一致的疫苗接种和监测数据，并且GIII向GI的转变发生在一个明确的时间段内时，日本脑炎病毒感染人类的病例数在统计学上有显著下降。我们的研究结果进一步支持了GI在感染作为终末宿主的人类方面效果较差这一观点。然而，需要进行实验研究来证实这一假设。该研究强调了采用替代方法调查疫情的价值，以及有效数据收集对疾病监测和控制的重要性。
