A21 Retrospectively describing hepatitis C virus transmission dynamics and tracking HCV transmission networks in real-time for strategic elimination interventions

Despite impressive uptake of direct acting antivirals for hepatitis C virus (HCV) in the Netherlands among HIV/HCV co-infected men who have sex with men (MSM), HCV transmission continues, especially among patients previously successfully treated for HCV. The incidence of reinfection occurs at the extremely high rate of 15 per 100 person-years. Clearly, more sophisticated methods are necessary to identify the sources and timing of new HCV infections among MSM. The aim of this research is to phylogenetically characterize HCV transmission dynamics within MSM-specific networks in order to provide a solid base for targeted interventions to monitor, control, and eventually stop the ongoing transmission of HCV among HIV-infected MSM and to prevent further spread of HCV to the community at large. The methodology that will be used is two-fold. Firstly, it concerns setting up a real-time monitoring system to track the HCV epidemic using phylogenetic tools and open-source software from http://nextstrain.org. Secondly, several phylogenetic methods will be used to retrospectively identify transmission clusters in Amsterdam and define epidemiological characteristics, including the directionality of transmission and the size and introduction dates of the clusters. This means that cluster cut-off points will have to be calculated. This research will result in a web-based molecular surveillance tool to monitor the persistence of endemic clades, emergence of new clades, and transmission clusters in ‘real time’, which, combined with clinical and epidemiological data, will be used for targeted interventions. The surveillance tool will be based on the open-source software from nextstrain.org. Secondly, by retrospectively describing the HCV transmission clusters in terms of introduction dates and subsequent dynamics, we may be able to better predict the future dynamics of the different clusters. High-resolution viral sequencing will allow us to identify the source and timing of (new) HCV infections and follow the trajectory of these MSM-specific lineages through the MSM population. Real-time insight in transmission networks using a web-based molecular surveillance tool will identify key targets for rapid interventions, awareness campaigns, and testing strategies. This can be used to prevent further spread to HIV-negative MSM and to control and eventually eliminate HCV from the MSM population.