The work proposed in this Project builds on our experience as a Center, and on the experience of the MIDAS network more generally, in modeling work involving policy makers, public health surveillance teams, and others who work to improve the quality of decisions by informing them with the best evidence available. The structure of our entire proposal reflects the view that transmission-dynamic models are tools that interpret raw data to produce evidence that can be used to make informed decisions (information flow upward in Figure P-1, taken from our policy summary ofthe experience with H1N1 pandemic influenza). The MIDAS network has spearheaded progress in improving the size, speed, and level of detail of transmission-dynamic models and other models for infectious diseases. While we will continue to press forward on that front, many of the other activities proposed for CCDD are motivated by the relative lack of attention to date to rigorous research on how model structure and parameter values should be informed by data, and in particular by new sources of data like genomics and participatory surveillance that will become increasingly available in the future. In this Policy Studies section, we propose first a series of symposia that will focus on particular aspects of the modeling process, especially the "upstream" (data->model structure and parameters) aspects, and we will invite decision makers to these symposia and involve them as much as possible in the presentations and discussions. We will write one or more papers summarizing the findings from each symposia, so that the outputs will be available to those who do not attend. We will also video record these symposia for web viewing. In addition, we plan two very different projects motivated by issues that have arisen during the current grant period. First, we will write a philosophical paper on the broad question of how models can be used to motivate decisions, focused on how the assumptions of the model can be designed to be "conservative" with respect to the decision being made. In a very different vein, we consider the issue of the overlap among transmission modeling, bioethics and biosafety as applied to a case study: Gain of Function (GOF) experiments involving highly pathogenic avian influenza viruses, an area on which we have already been active.