The new edition of this book is an outgrowth of an independent research center established by the United States Department of Homeland Security and the Environmental Protection Agency, dedicated to advancing laboratory techniques, creating mathematical tools, and developing datasets needed to improve Quantitative Microbial Risk Assessment (QMRA).  This book looks at the latest methodologies to quantify at every step of the microbial exposure pathways, from the first release of a pathogen to the actual human infection.   It provides techniques on how to  gather information, on how each microorganism moves through the environment, how to determine their survival rates on various media, and how people are exposed to the microorganism (i.e. skin contact, inhalation, or ingestion).  The book explains how these measurements can give us a comprehensive view of how environmental contamination (deliberate or accidental) can lead to human infection and reveals key points where interventions can be employed to save lives.  Since QMRA allows the reader to incorporate interventions into risk estimates, the book explains how QMRA can be used as a tool to measure the impact of interventions and identify the best policies and practices to protect public health and safety.