Tick-Borne Encephalitis Virus (TBEV) is a dangerous arbovirus widely distributed in Northern Eurasia. The area of this pathogen changes over time. At the beginning of the 2000s, the Ixodes tick populations in Karelia increased. At the same time, the area of I. persulcatus, the main vector of the Siberian TBEV subtype, also expanded. Herein, we sequenced 10 viruses isolated from ticks collected in three locations from the Karelia region in 2008–2018. PCR positive samples were passaged in suckling mice or pig embryo kidney cells (PEK). After the second passage in suckling, mice viral RNA was isolated and E-gene fragment was sequenced. Viral sequences were expected to be similar or nearly identical. Instead, there was up to a 4.8% difference in nucleotide sequence, comparable with the most diverse viruses belonging to the Baltic subgroup in Siberian TBEV subtype (Baltic TBEV-Sib). To reveal whether this was systemic or incidental, a comprehensive phylogeographical analysis was conducted. Interestingly, viruses within each geographic region demonstrated comparable diversity to the whole Baltic TBEV-Sib. Moreover, Baltic TBEV-Sib has a distribution area limited by three ecological regions. This means that active virus mixing occurs in the vast geographic area forming one common virus pool. The most plausible explanation is the involvement of flying animals in the TBEV spread.

中文翻译：

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波罗的海集团T虫脑炎病毒系统：遗传和地理距离之间的系统不一致模式

Tick-Borne脑炎病毒（TBEV）是一种危险的虫媒病毒，广泛分布于北欧亚大陆。该病原体的面积随时间变化。在2000年代初，卡累利阿的x虫数量增加。同时，西伯利亚TBEV亚型的主要载体persulcatus的面积也扩大了。在本文中，我们对2008-2018年从卡累利阿州三个地点收集的tick中分离出的10种病毒进行了测序。PCR阳性样品在乳鼠或猪胚肾细胞（PEK）中传代。哺乳期第二次传代后，分离小鼠病毒RNA，并进行E-对基因片段进行测序。预期病毒序列相似或几乎相同。相反，与西伯利亚TBEV亚型（Baltic TBEV-Sib）中属于波罗的海亚组的种类最多的病毒相比，核苷酸序列差异高达4.8％。为了揭示这是系统性还是偶然性，进行了全面的系统地理分析。有趣的是，每个地理区域内的病毒都表现出与整个波罗的海TBEV-Sib相当的多样性。此外，波罗的海TBEV-Sib的分布区域受到三个生态区域的限制。这意味着主动病毒混合发生在形成一个普通病毒库的广阔地理区域中。最合理的解释是飞行动物参与了TBEV传播。