David Waltner-Toews is a specialist in the epidemiology of food and waterborne diseases, zoonoses (diseases other animals share with people) and ecosystem health. He is a professor in the Department of Population Medicine at the University of Guelph. He has worked in many countries, including Canada, India, Nepal, Indonesia, Kenya, Uganda, Guatemala, and Peru. www.ovc.uoguelph.ca/popmed/ecosys/index.html