Viral infections are a major burden to public health and have a significant socioeconomic impact in the European Union, both through direct disease-associated, but also through indirect costs, most notably loss of labor. Positive-strand RNA (+RNA) viruses are the largest group of human pathogens, comprising viruses causing from severe life-threatening infections such as hepatitis C or SARS over emerging tropical diseases such as Dengue or Chikungunya fever to self-limiting but nonetheless ubiquitous infections such as the common cold or gastro-intestinal infections. For by far the most of these viruses, no vaccines or direct acting antiviral treatments are available, constituting an urgent socioeconomic need in Europe and worldwide. Due to the very limited coding capacity of their genome, RNA viruses strongly depend on host cell functions. The limited number of virus-encoded proteins that can serve as antiviral drug targets and the high mutation rate of RNA viruses, potentially leading to the rapid development of drug resistance, complicate the development of compounds that target viral functions directly and effectively. However, the strong dependency on host cell processes opens up alternative possibilities to inhibit viral replication by interfering with host factors and pathways. Besides a much larger number of potential drug targets, this more indirect approach has the added benefit of a high barrier to resistance, i.e. it is unlikely that the virus can easily escape treatment by acquiring a single point mutation (in contrast to a point mutation at e.g. a drug binding site that could make a virus resistant to a direct-acting antiviral). SysVirDrug aims to identify essential host cell functions, on which all investigated +RNA viruses (and potentially others) critically depend, and to devise strategies to pharmacologically interfere with their function in viral replication. The consortium covers a panel of five diverse and highly relevant plus-strand RNA viruses, including hepatitis C virus, dengue virus, chikungunya virus, SARS-coronavirus and enterovirus (coxsackievirus B3). Using a true systems biology approach, combining available high-throughput experimental data to identify relevant host processes by sophisticated bioinformatics analyses, mechanistic mathematical modeling and detailed quantitative and time-resolved experimentation, SysVirDrug will identify the most sensitive panviral load- and choke points of intracellular replication. Based on an integrative, network-based analysis of published and our own unpublished high-throughput RNAi-screening data, we will identify relevant host processes affecting viral replication in the panel of studied +RNA viruses. Mathematical models of viral replication will be set up based on quantitative, time resolved experimentation, integrating relevant host factors through mechanistic modeling. Models will be iteratively validated and refined and sensitivity analyses will identify the most vulnerable interference points in the developed models as putative targets for antiviral intervention. We hypothesize that targeting common, sensitive host pathways will result in panviral inhibition of replication. We are going to test this hypothesis by silencing relevant genes in implicated pathways or by employing pharmacological inhibitors and assaying for an impact on replication over the full panel of investigated +RNA viruses. Through the involvement of a commercial partner, SysVirDrug will identify and develop small molecule inhibitors of the identified host pathways, which will be translated into marketable pharmaceutical lead compounds. Throughout the entire project, relevant industry users will be integrated through a scientific advisory board, as well as a series of industry workshops and contacts. Through the further integration of an experienced Technology Transfer partner, SysVirDrug will translate cell biological and virological knowledge obtained through iterative cycles of experiment, bioinformatics and mathematical modeling into socioeconomically relevant, industrially exploitable ?antivirotics?, with direct benefits for health and wellbeing in Europe and beyond.