This news item is about: Why in the world are the National Institutes of Health (NIH) funding a veterinary epidemiologist to study Clostridium difficile (CDI), the leading cause of infectious diarrhea in human hospitals? Yrjo Grohn, Professor of Epidemiology and Chair of the Department of Population Medicine and Diagnostic Sciences, has traditionally conducted research on common food-borne pathogens, such as salmonella, listeria, and e-coli, in farm animal populations. Like many food supply epidemiologists, Grohn used mathematical modeling to understand the spread of these infectious agents as a means of optimizing food production systems. His work helped producers operate efficiently while keeping the risk of economic loss and zoonotic transmission (animal to human) within acceptable limits. Now, Grohn and his colleagues have found an important new application for their empirical animal models – the study of infectious disease in human populations.