Biomedical problems are innately complex, and real solutions will require input from many fields. Such input is most effective if it is integrated int an interdisciplinary framework, with a convergence of approaches that truly merges expertise into a more seamless form of collaboration. The foundation of a convergence in interdisciplinary research is a strong modeling framework because modeling is the language that can cross disciplines and levels of biological organization. The Center for Modeling Complex Interactions will create the intellectual, cultural, and physical environment to foster convergence in interdisciplinary biomedical research. The Specific Aims are: (1) Conduct model-based, interdisciplinary research that leads faculty to transition to independence. The three initial projects will focus on viral co-infection. Co-infection is common in nature and yet understudied in the laboratory. Co-infecting viruses can interact directly or indirectly, and may have nonlinear effects on viral expression and on host outcomes. Project 1 examines disease severity during co- infection in a mouse model system. Project 2 establishes an invertebrate system to examine co-infection at multiple levels of biological organization. Project 3 uses agent-based modeling to examine transmission dynamics at the population level. (2) Establish a collaborative and synergistic Modeling Core to impel interdisciplinary research and to build institutional research capacity. Mathematical modeling is central to interdisciplinary research because it plays a role in every phase of the research, from hypothesis formulation to experimental design, from data analysis to interpretation. Most importantly, it can reveal connections between data from seemingly unrelated areas and across all levels of biological organization, opening new areas of scientific inquiry. Our Modeling Core is a service core that accepts research projects and delivers models, modeling strategies, and connections between projects. (3) Expand participation in interdisciplinary biomedical research. This will be achieved by redirecting vacant and new faculty positions, providing pilot grants to engage current faculty, and outreach to the regional medical community. The plan for long-term sustainability is to first gain credibility withn the university and greater scientific community; next, build research capacity by attracting a diverse group of current and incoming faculty to engage in research in the Center; and, finally, to establish the Center as a research 'entity' within the structure of the University of Idaho.