The contribution of injection drug use to hepatitis C virus transmission globally, regionally, and at country level: a modelling study

June 2019
Trickey, A., Fraser, H., Lim, A. G., Peacock, A., Colledge, S., Walker, J. G. ,Leung, J., Grebely, J., Larney, S., Martin, N. K., Hickman, M., Degenhardt, L., May, M. T., & Vickerman, P. (2019). The contribution of injection drug use to hepatitis C virus transmission globally, regionally, and at country level: a modelling study. The Lancet Gastroenterology & Hepatology, Advance online publication. doi:10.1016/s2468-1253(19)30085-8

The World Health Organization (WHO) aims to eliminate the hepatitis C virus (HCV) as a public health threat by 2030. Injection drug use is an important risk factor for HCV transmission, but its contribution to country-level and global epidemics is unknown. The authors estimated the contribution of injection drug use to risk for HCV epidemics globally, regionally, and at country level. The modelling suggests that stepping up efforts to prevent transmission of hepatitis C among people who inject drugs, could reduce future infections by 43 per cent globally, according to modelling by researchers at the University of Bristol and the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney.

People who inject drugs are at high risk of becoming infected with the hepatitis C virus through the sharing of needles, syringes and other injecting drug equipment. While the percentage of people with hepatitis C is estimated to be less than one per cent in most countries, the percentage of people who inject drugs with hepatitis C tends to be over 30 per cent.  

The researchers used mathematical modelling to estimate how much the sharing of equipment for injecting drug use contributes to the hepatitis C epidemics for 88 countries, which account for 85 per cent of the world’s population. They estimated that, if hepatitis C transmission due to the risk associated with injecting drug use was removed, around 43 per cent of all infections up to 2030 would be prevented globally.

Seventy-nine per cent of hepatitis C infections could be prevented in high-income countries and 38 per cent of infections in low- and middle-income countries. These estimates range from two per cent in Nigeria to 100 per cent in several countries, including Iceland and Finland, with estimates of 98 per cent for the UK and 77 per cent for the USA and 62 per cent for Australia.

The authors note that the figure for Australia, like Spain (31 per cent) and Greece (23 per cent) is lower than expected. This discrepancy could be attributable to data issues or HCV-epidemic factors—e. g, historically high levels of injection drug use that have now decreased, underestimates for the prevalence of people who inject drugs, or possibly high numbers of migrants with higher HCV risk than the background population.