Eastern Guangdong is a Teochew dialect
Eastern Guangdong is a Teochew dialect area. We found that subtype 1b (3.1%) in this region was significantly lower than in other areas. Subtype 1b began its spread from the central part of China out into the whole country through illegal blood donation in the mid-1990s (Lu et al., 2013) and is now the main epidemic subtype in the general Caspase-3 Fluorometric Assay Kit of China (Huang et al., 2018; Lu et al., 2005). Subtype 1b is also the main subtype found in unpaid blood donors in Guangdong Province (Rong et al., 2014). Usually the proportion of 1b in DU is very low (Tian et al., 2012; Wan et al., 2016). This pattern of spread from north to south may be the reason that 1b is low in the eastern region. In contrast, the proportion of subtype 1b in Jiangsu (23.8%) (Lu et al., 2018) and Anhui (11.8%) (Cui et al., 2017) DU is not low, suggesting that the same subtype may have different modes of transmission between the eastern and southern regions of China. Although another study (Chen et al., 2011) showed that the percentage of subtype 1b (10.7%) is higher than that in our study (6.7%). The probable reason for this is the differences in the study participants. The study conducted by Chen et al. (Chen et al., 2011) included study participants who were patients from two hospitals in Guangzhou and Shenzhen. We compared the 1b in Guangzhou and Shenzhen in our study with that 2011 study and found that there was a very slight difference between their data (10.7%) and ours (10.6%). Unexpectedly, contrary to the situation of 1b, the prevalence of subtype 6a in the eastern region (67.2%) is the highest, even higher than that in the PRD (63.7%). Subtype 6a is widespread among drug users, suggesting that the eastern region may be the epidemic source of 6a in Guangdong. In western Guangdong, three of the four cities border Guangxi. We found that in western Guangdong subtype 3a was significantly less common than in other regions. Meanwhile the proportion of subtype 3a in Guangxi was low (Garten et al., 2005; Tian et al., 2012), suggesting that HCV prevalence in the western region was closely related to that in Guangxi. In contrast, in the PRD subtype 3a was the most common suggesting that 3a in PRD probably was originated from different source. Previous studies have shown that 3a was introduced to southwestern China through DU. A study of HIV/HCV co-infections in Guangxi found that 3a was not found in IDU, but was found in a small number of sexually transmitted infectors (5.9%) (Tian et al., 2012), suggesting that the mode of transmission of 3a may have changed, and the sexually transmitted population has also become an important group of people who can spread HCV subtype 3a. Migrant workers also affect the HCV subtype distribution in Guangdong and other provinces. In this study, the non-Guangdong residents DU accounted for 14.9%, mainly from Guangxi (44.8%) and Hunan (22.1%). Guangxi borders western Guangdong while Hunan borders northern Guangdong and both were the main provinces exporting migrant workers to Guangdong. There were significant differences in the distribution of subtypes between the Guangdong DU and the non-Guangdong DU. Among the infected DU from Guangxi, subtype 6a predominated (53.9%), followed by 3b (23.1%). Additionally, the main subtypes in Guangxi IDU were also 6a (35.6%) and 3b (32.9%) (Tian et al., 2012), suggesting that Guangxi DU have an impact on HCV subtype distribution in Guangdong. The subtypes among DU from Hunan are similar to those in Guangxi, with 6a being the most prevalent (46.9%), followed by 3b (28.1%). Interestingly, 6a is not the main HCV epidemic subtype in Hunan (Huang et al., 2018), suggesting that Hunan DU may get infected in Guangdong and then they bring subtype 6a into Hunan Province with them upon their return home. In the past, we had no idea of the HCV subtypes of NIDU. In this study, we compared the subtypes between IDU and NIDU and found no significant differences between them, which is both similar (van den Berg et al., 2009), and different to previous data (Tao et al., 2015). There may be two reasons for this. First, some NIDU may not have answered the questionnaire truthfully regarding their drug use patterns. Second, the HCV of NIDU is connected with IDU in some other ways, probably by sexual transmission. It has been reported that sexual risk factors such as multiple partners, commercial partners, and a lack of condom use, were significantly between IDU and NIDU (Xia et al., 2008). Our study shows that there was no significant difference between IDU and NIDU in terms of condom use either with legal or commercial partners.