AbstractThe first human infection with severe fever with thrombocytopenia syndrome virus (SFTSV) was detected in Shaanxi Province, China, in 2013, although the virus had been reported in 13 other provinces of China since 2010. We collected and analyzed a total of 4,011 samples, including 936 human serum samples, 155 animal serum samples, 895 ticks, 1,950 mosquitoes, 30 midges, and 20 sandflies. SFTSV antibodies were found in 44 human samples (4.7%) with no significant differences between males and females or across counties. The incidence rate of severe fever with thrombocytopenia syndrome was significantly higher among individuals 20-60 years of age. Moreover, SFTSV-specific antibodies were detected in goats (66.7%), cattle (13.2%), and dogs (15.0%), but not in pigs (0%). We detected the virus in Haemaphysalis concinna ticks with a prevalence rate of 21.3% (17/80 pools). All mosquito, midge, and sandfly samples were negative for SFTSV. These results support wide circulation of the virus in western China. Haemaphysalis concinna ticks may serve as a novel SFTSV vector, and the role of these ticks requires further investigation.