Emergence of Novel Psychoactive Substance injecting associated with rapid rise in the population prevalence of hepatitis C virus

Background Novel Psychoactive Substance (NPS) use has increased in recent years and generated significant concern within public health. People who inject drugs (PWID) are at increased risk of blood borne viruses, in particular Hepatitis C virus (HCV). However, little is known about the extent of NPS injecting at a national level and its association with HCV. This study provides one of the first epidemiological analyses of the association between NPS injecting and HCV among a population level sample of PWID. Methods Five cross sectional surveys of almost 13,000 PWID attending services providing injecting equipment across Scotland between 2008 and 2016 were analysed. Logistic regression was used to determine associations between NPS injecting and HCV. Results The proportion of PWID reporting that they had injected NPS in the previous six months increased from 0.2% in 2008–09 to 11.0% in 2015–16. Those who reported injecting NPS were considerably more likely to be resident in the Lothian NHS Board area at the time of the study (AOR 5.6 (95% CI 4.1–7.5)) and to have had recent experience of homelessness (AOR 1.4 (95% CI 1.0–1.9)). People who injected NPS were also significantly more likely to be HCV positive (AOR 1.7 (95% CI 1.2–2.4)). In Lothian, HCV prevalence rose from around 30% between 2008 and 2012 to 41% and then 48% in 2013–14 and 2015–16 respectively. Increases in prevalent HCV infection in Lothian may be partly attributed to increases in NPS injecting. Conclusion In Scotland, people who had injected Novel Psychoactive Substances were at increased risk of hepatitis C virus. Novel Psychoactive Substance injecting poses a threat to HCV elimination strategies.