The risk of human- and mammal-infecting tick-borne viruses in Northwest China and adjacent countries

The prevalence, evolution, and disease risk of pathogenic tick-borne viruses (TBVs) remains poorly understood in northwest China and adjacent countries, which are endemic for several TBVs of public health importance. Herein, we perform meta-transcriptomic sequencing of >9,600 ticks collected across this vast geographic area to identify 92 RNA viruses and assemble 1,567 viral genomes from 28 different tick species, including ten human- and mammal-infecting TBVs. Tacheng tick virus 1 (TcTV-1), Tacheng tick virus 2 (TcTV-2), Tamdy virus (TAMV), and Crimean-Congo hemorrhagic fever virus (CCHFV) are the most common human-infecting TBVs. We also report several pathogenic TBVs that are not identified in China (Burana virus and Bhanja virus), Kazakhstan (TcTV-1), and northwest China (Wad Medani virus and Alongshan virus) before. We predict a significant increase in the number of high-risk regions for the four major tick vectors of pathogenic TBVs, and the distribution of TAMV, TcTV-1, TcTV-2, and CCHFV, with 65.4% of the counties in this region identified as high risk for CCHFV. Therefore, the real disease burden caused by TBVs in northwest China and adjacent countries may be underestimated than appreciated, and we therefore call for strengthened field surveys and epidemiological surveillance in this vast region.

在中国西北及周边国家，致病性蜱传病毒（tick-borne viruses, TBVs）的流行特征、演化进程与致病风险仍未得到充分阐明；该区域是多种具备公共卫生重要性的蜱传病毒的自然疫源地。本研究对该广袤地理范围内采集的9600余只蜱开展宏转录组测序，共鉴定出92种RNA病毒，并从28个不同蜱种中组装得到1567条病毒基因组，其中包含10种可感染人类与哺乳动物的致病性蜱传病毒。塔城蜱病毒1型（Tacheng tick virus 1, TcTV-1）、塔城蜱病毒2型（Tacheng tick virus 2, TcTV-2）、坦迪病毒（Tamdy virus, TAMV）以及克里米亚-刚果出血热病毒（Crimean-Congo hemorrhagic fever virus, CCHFV）是最为常见的可感染人类的致病性蜱传病毒。本研究还报道了此前未在中国境内（布拉纳病毒、班贾病毒）、哈萨克斯坦（塔城蜱病毒1型）以及中国西北区域（瓦德迈达尼病毒、阿尔山病毒）被检出的多种致病性蜱传病毒。本研究预测，致病性蜱传病毒的四种主要蜱媒宿主的高风险分布区域，以及坦迪病毒、塔城蜱病毒1型、塔城蜱病毒2型与克里米亚-刚果出血热病毒的传播范围均将显著扩张；该区域内65.4%的县域被判定为克里米亚-刚果出血热病毒的高风险流行区。由此可见，中国西北及周边国家由致病性蜱传病毒所引发的实际疾病负担可能远高于此前的评估，因此本研究呼吁在该广袤区域内强化实地调查与流行病学监测工作。