Theresa Stocks: Dynamic modelling of hepatitis C transmission among injecting drug users: revealing the undiagnosed and impact of interventions

Abstract: To reach the WHO goal of hepatitis C elimination by 2030, it is essential to identify the number of undiagnosed cases and to investigate the impact of interventions such as drug treatment and needle exchange programs on the disease transmission dynamics. In most developed countries, the primary route of hepatitis C transmission is via contaminated needles shared by injecting drug users (IDUs). However, high uncertainty regarding the size of the IDU population and difficulty detecting hepatitis C in the early stages of the disease make it challenging to estimate the number of undiagnosed cases. We present a novel, multi-layered dynamic transmission model for hepatitis C transmission within an IDU community that accounts for disease stage (acute and chronic), IDU status (current and former IDU), status of diagnosis (diagnosed and undiagnosed) and country of disease acquisition (within or outside the country under consideration). First, based on this model and using routine surveillance data, we estimate the number of undiagnosed IDUs, the basic reproduction number, the time until diagnosis and associated uncertainties. Second, we examine the impact of two interventions on disease dynamics: 1) direct-acting antiviral drug treatment, which is characterized by high success rates but substantial costs, and 2) needle exchange programs. We illustrate our approach for Swedish data, however, our modelling approach can also be applied to other countries with a similar disease burden. To support communication of our results with public health decision makers, the model and its outputs are made accessible through a shiny app. This is joint work with Leah Martin, Sharon Kuhlmann-Berenzon and Tom Britton and work in progress.