Disease spread modeling: A decision tool for veterinary public health

Foreign animal diseases (FADs) are those that have the ability for rapid epidemic spread and convey important economic, trade, and food security consequences. Some FADs are also zoonotic and incursions of those FADs into new areas pose a potential public health threat. To minimize the negative effects of an FAD incursion and return to a disease free status as quickly as possible, it is critical that the United States be prepared to mount an effective response; however, the complexity of U.S. agricultural systems combined with a lack of recent practical experience with many FADs present challenges for response planners. Epidemiologic simulation models provide simplified representations of complex systems and are valuable tools that can be used to investigate the characteristics of disease spread and the effectiveness of potential control strategies. The North American Animal Disease Spread Model (NAADSM) is a free, publicly available decision tool that was developed through an international collaborative effort of government and academic institutions. NAADSM provides a framework for the development of epidemiologic models that can simulate the spread and control of a variety of infectious diseases. NAADSM can be applied to questions regarding the consequences of an FAD introduction in terms of numbers of infected herds and animals, the potential effectiveness of disease control measures, and the potential impacts of resource limitations on disease control. The utility of epidemiologic models and the capabilities of NAADSM will be demonstrated using examples from studies that simulated the spread of foot-and-mouth disease and highly pathogenic avian influenza.