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 >9600 ticks collected across this vast geographic area to identify 92 RNA viruses and assemble 1567 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 detected. We also report several pathogenic TBVs not previously identified in China (Burana virus and Bhanja virus), Kazakhstan (TcTV-1), and northwest China (Wad Medani virus and Alongshan virus). 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 more underestimated than appreciated, and we call for strengthened field surveys and epidemiological surveillance in this vast region.