the North American Animal Disease Spread Model (NAADSM) in conjunction with data, statistical methods, and references from scientific literature. Simulation outputs from NAADSM were used to evaluate the impact of FMD spread through Kansas and into six adjoining states in different release events. The analysis estimated the consequences of large epidemics and the potential effects of some mitigation measures on an epidemic. Depending on the risk scenarios, the outputs suggested that an epidemic in the seven states could last 18 months or more and result in the loss of tens of millions of animals. The 2010 SSRA results were criticized by the previous National Research Council committee for a lack of transparency, structural limitations in NAADSM, and some specific modeling choices (NRC, 2010). The uSSRA makes a variety of changes and attempts to address all the previously identified shortcomings of the 2010 SSRA. The revised model in the uSSRA now estimates an FMD epidemic in these seven states to last about twice as long as and affect several times more animals than the 2010 SSRA.
The overall methodology and presentation of epidemic modeling in the uSSRA are substantially improved compared to those in the 2010 SSRA. Part of the reason is the uSSRA’s better description of model limitations and uncertainty. Issues of reliability, uncertainty, and sensitivity are acknowledged at the beginning of Section 6 of the uSSRA and addressed again throughout. The breadth of epidemiological material collected in the uSSRA could make it a useful reference for future FMD research and planning.
However, the epidemic modeling in the uSSRA still provides only a limited picture of the likely possibilities involved in an FMD epidemic originating in Manhattan, Kansas. Some of the limitations result from inadequacy of available tools, including NAADSM, some from lack of data and incomplete scientific understandings, and some from incomplete characterization of the resources and capacity for mitigation responses. Practical considerations have imposed a number of those limitations, as the uSSRA acknowledges. The committee finds that the modeling results underestimate the absolute size and duration of epidemics, in part because of a number of specific assumptions used in the uSSRA. Overly optimistic assumptions were made about response resources and capacities anticipated to be available by 2020, and these in turn would lead to an underestimation of the magnitude, duration, and economic impact of an FMDv escape from the NBAF in Manhattan, Kansas. The uSSRA underestimated contact risks and used overly optimistic parameter values for diagnostic capabilities, surveillance, contact rates, vaccination, and response. Consequently, the uSSRA spread model results incorrectly indicate foreshortened spread and low impact estimates. The incomplete data on interstate direct contacts,