The contribution of injecting drug use as a risk factor for Hepatitis C virus transmission globally, regionally, and at country level: a modelling study

Background

The World Health Organization aims to eliminate the hepatitis C virus as a public health threat by 2030. Injecting drug use is an important risk factor for hepatitis C virus transmission, but the contribution to country-level and global epidemics is unknown. We estimated the contribution of injecting drug use-associated risk to hepatitis C virus epidemics at country and global levels.

Methods

A dynamic, deterministic hepatitis C virus transmission model was used to simulate hepatitis C virus epidemics at country-level among people who inject drugs and the general population. Each country’s model was calibrated using country-specific data from UN datasets and systematic reviews on the prevalence of hepatitis C virus and injecting drug use. The population attributable fraction of hepatitis C virus transmission (the transmission population attributable fraction) associated with injecting drug use was estimated, defined here as the percentage of hepatitis C virus infections prevented if additional hepatitis C virus transmission due to injecting drug use was removed between 2018-2030.

Results

The model included 88 countries, comprising 85% of the global population. The model predicted that in 2017 0.2% of individuals in those countries were people who inject drugs and 8% of prevalent hepatitis C virus infections were among people who had recently injected drugs. Globally, if elevated hepatitis C virus transmission risk among people who inject drugs was removed, an estimated 43% (95% credibility interval [CrI]: 24%-66%), the transmission population attributable fraction, of incident hepatitis C virus infections would be prevented from 2018-2030, varying regionally. The transmission population attributable fraction was higher (79%, CrI: 56%-97%) in high-income countries than low- and middle-income countries (38%, CrI: 22%-63%) and was associated with the percentage of a country’s prevalent infections that are among people who inject drugs.

Conclusions

Unsafe injecting practices among people who inject drugs contribute substantially to incident infections globally; any intervention that can reduce transmission among people who inject drugs will have a pronounced effect on country level incidence.