The number of poly-drug users who mix use heroin and synthetic drugs (SD) is increasing worldwide. The objective of this study is to measure the risk factors for being infected with hepatitis C (HCV), human immunodeficiency virus (HIV) and syphilis among SD-only users, heroin-only users and poly-drug users. A cross-sectional study was conducted in 2015 from a national HIV surveillance site in Southwest China, 447 poly-drug, 526 SD-only and 318 heroin-only users were recruited. Poly-drug users have higher drug-use frequency, higher rates of drug-sharing and unsafe sexual acts than other users (p < 0.05). About a third (36.7%) of poly-drug users experienced sexual arousal due to drug effects, which is higher than the rate among other drug users. Poly-drug users had the highest prevalence of HIV (10.5%) and syphilis (3.6%), but heroin-only users had the highest prevalence of HCV (66.0%) (all p < 0.05) among three groups. Logistic regression shows among poly-drug users, having sex following drug consumption and using drugs ≥1/day were the major risk factors for both HIV (Adjusted odds ratio (AOR) = 2.4, 95% CI [1.8–3.4]; 2.3, [1.6–3.1]) and syphilis infection (AOR = 4.1, [2.1–6.9]; 3.9, [1.8–5.4]). Elevated risk of both HIV and syphilis infection have been established among poly-drug users.

ObjectiveTo describe the differences in sexual practices among individuals with various drug administration patterns.SettingA detoxification centre in Southwest China, a part of the Chinese national sentential surveillance network for hepatitis C virus (HCV), HIV and syphilis infections, was recruited.ParticipantsA total of 610 newly enrolled injection drug users (IDUs) from detoxification centre were included during 2015.Primary and secondary outcome measuresSelf-reported sexual activities, drug-related practices and laboratory-confirmed HCV, HIV and syphilis infection status were collected.ResultsOf the 610 IDU, 295 (48.4%) used heroin only, 277 (45.4%) poly-drug users reported the mixed use of synthetic drugs (SDs) with heroin and 38 (6.2%) used SDs only. The average daily drug injection frequency for poly-drug users (3.3±1.2 times) was the highest, followed by heroin-only (2.2±0.8 times) and SD-only users (1.2±0.4 time). SD-only drug users reported the highest proportion (86.8%) of engaging in sexual activities in the previous month, with more than half (54.5%) reporting any condomless sex. A higher frequency of daily injecting in heroin-only users was significantly correlated with the less likelihood of sex, condomless sex in the past month, having sex with fixed partners, condomless commercial sex in the previous 12 months (all p<0.01). In poly-drug users, who injected drugs two times per day was associated with the highest proportion of people who engaged in sex and commercial sex (p<0.05). For SD-only users, increased drug use was not associated with reducing sexual risk (p>0.05). Different patterns of HCV, HIV and syphilis infections prevalence rates were shown among the IDU depending on the roles and length of exposure.ConclusionsThe daily drug injecting frequency of heroin-only and poly-drug users was negatively associated with sexual activities, but SD-only users kept a high frequent engagement in sex. The interventions for relevant diseases should adapt to characteristics of IDU.