Fig. 1

The map showing sampling spots in Ningxia and 17 provinces or municipalities in China, from which HCV reference sequences were included in the phylogenetic analysis. The 17 provinces and municipalities were divided into five regions and colored accordingly: the northwest (Xinjiang, Qinghai, Shaanxi), north & northeast (Liaoning, Beijing, Shanxi), southeast (Shanghai, Zhejiang, Jiangxi, Fujian), central south (Hubei, Hunan, Guangdong, Hainan), and southwest (Sichuan, Yunnan, Guangxi). Ningxia is located in northwest China, with six cities Shizuishan (SZS), Yinchuan (YC), Wuzhong (WZ), Zhongwei (ZW), Tongxin (TX), and Guyuan (GY) scattered from north to south where participants were recruited. Major drug trafficking routes were shown by grey arrows referring to Sullivan et al. 2007, which originated from Yunnan (bordering Myanmar and Laos) and Xinjiang (bordering Afghanistan and Pakistan), respectively [39]