Project Summary Non-cholera Vibrio species, such as V. parahaemolyticus, are often an underlying cause of seafood-associated illnesses leading to an estimated 80,000 illnesses, 500 hospitalizations and 100 deaths annually in the United States. Shellfish, which are often consumed raw or undercooked, can accumulate a wide array of infectious pathogen including bacteria, making them a primary exposure route for non-cholera Vibrio infections. As shellfish aquaculture continues to grow in the United States, there is a need for more reliable Vibrio detection methods in harvesting waters in order to better quantify human health risks from these bacteria and to limit the burden of vibriosis. The goals of this research are to characterize levels of Vibrio parahaemolyticus bacteria in estuarine environments and to assess human health risks from this emerging pathogen. Methods developed will be built upon a unique opportunity to work with comprehensive data sets from two large estuarine environments, the Chesapeake Bay and the Puget Sound, which represent two of the most significant economic estuarine systems on the East and West coast of the US. Quantitative analyses will focus on the advancement of spatial and spatial-temporal statistical methods to better quantify uncertainty for spatially predicting in estuarine environments. Statistical results will be used to support the development of a region-specific quantitative microbial risk assessment (QMRA) for vibriosis, extending the Food and Drug Administration's (FDA's) current national risk assessment model. The Puget Sound database includes Vibrio outbreaks traced back to specific harvesting areas, information that will be used to develop a novel dose-response model for the risk assessment. Results of this research will provide reliable tools that can be used to improve risk management procedures for infections from Vibrio parahaemolyticus in both these bodies of water, as well as applications to other estuaries that support shellfish harvesting, leading to increased estuarine economic output, reduced disease burden, and improved public health.