PDF(Pubmed)
Abstract：
Since the reemergence of St. Louis Encephalitis (SLE) Virus (SLEV) in the Southwest United States, identified during the 2015 outbreak in Arizona, SLEV has been seasonally detected within Culex spp. populations throughout the Southwest United States. Previous work revealed the 2015 outbreak was caused by an importation of SLEV genotype III, which had only been detected previously in Argentina. However, little is known about when the importation occurred or the transmission and genetic dynamics since its arrival into the Southwest. In this study, we sought to determine whether the annual detection of SLEV in the Southwest is due to enzootic cycling or new importations. To address this question, we analyzed 174 SLEV genomes (142 sequenced as part of this study) using Bayesian phylogenetic analyses to estimate the date of arrival into the American Southwest and characterize the underlying population structure of SLEV. Phylogenetic clustering showed that SLEV variants circulating in Maricopa and Riverside counties form two distinct populations with little evidence of inter-county transmission since the onset of the outbreak. Alternatively, it appears that in 2019, Yuma and Clark counties experienced annual importations of SLEV that originated in Riverside and Maricopa counties. Finally, the earliest representatives of SLEV genotype III in the Southwest form a polytomy that includes both California and Arizona samples. We propose that the initial outbreak most likely resulted from the importation of a population of SLEV genotype III variants, perhaps in multiple birds, possibly multiple species, migrating north in 2013, rather than a single variant introduced by one bird.
摘要：
自从圣路易斯脑炎（SLE）病毒（SLEV）在美国西南部再次出现以来，在2015年亚利桑那州爆发期间发现，已在库蚊中季节性检测到SLEV。整个美国西南部的人口。先前的工作表明，2015年的爆发是由输入的SLEV基因型III引起的，以前只在阿根廷发现过。然而,自从进入西南地区以来，关于进口发生的时间或传播和遗传动力学知之甚少。在这项研究中,我们试图确定西南地区SLEV的年度检测是由于植物性循环还是新输入。为了解决这个问题，我们使用贝叶斯系统发育分析分析了174个SLEV基因组(142个测序作为本研究的一部分),以估计到达美国西南部的日期,并表征SLEV的潜在种群结构.系统发育聚类表明，自爆发以来，在Maricopa和Riverside县传播的SLEV变体形成了两个不同的种群，几乎没有证据表明县间传播。或者，看来，在2019年，尤马和克拉克县经历了起源于河滨和马里科帕县的SLEV的年度进口。最后,西南地区SLEV基因型III的最早代表形成了包括加利福尼亚州和亚利桑那州样本的多切除术。我们认为，最初的爆发很可能是由于输入了SLEV基因型III变异的人群，也许在多种鸟类中，可能是多个物种,2013年向北迁移，而不是一只鸟引入的单一变体。
