The Harvard Center for Risk Analysis (HCRA), part of the Harvard School of Public Health, performed an analysis for the U.S. Department of Agriculture to determine what the effects would be if “mad cow” disease were introduced into the United States. Mad cow disease, which is the popular term for bovine spongiform encephalopathy, has not been detected in the United States. What the HCRA researchers found is that there is little chance of mad cow disease spreading in the United States. The team was led by George Gray, acting director of the HCRA. Researchers Joshua Cohen and Silvia Kreindel, along with MIT doctoral student Keith Duggard, constructed a computer model to simulate the course of the disease should one or more sick animals be introduced to the United States herd. They ran several dozen scenarios through the model, generating one thousand variations for each scenario. The researchers ran simulations based on the introduction into the American cattle herd of one, five, 10, 20, 50, 200 or 500 sick animals. They found that in all cases, the disease fails to take hold and dies out, usually within a matter of a few years.