BY THOMAS M. YUILL AND B. C. EASTERDAY¹

THE PUBLIC, AS WELL AS the scientific community, is surprised and concerned about the periodic emergence of new infectious diseases. This concern has been fueled by recent outbreaks of Ebola virus disease in people in Zaire, Venezuelan equine encephalitis and fowl plague in Mexico, "mad cow disease" (bovine spongiform encephalopathy) in Europe, and the spread of avian cholera in wild waterfowl in North America. Bob Hanson would not have been surprised at all by these disease trends. He was familiar with "surprise" disease outbreaks. His career was built on determining where these surprise diseases came from, how they spread, and how they might be controlled.

Bob Hanson insisted that we should expect to see the emergence of new diseases as ecological and environmental conditions and host populations change. He operated on the basic premise that infectious agents must be viewed and attacked holistically because they are components of the ecosystems in which their hosts live. He recognized that no one person had all the expertise required to understand the natural history of diseases, and he was a champion of interdisciplinary team approaches. The problems on which he focused were always real ones that originated in nature.