Chronic wasting disease is laterally transmitted and environmental contamination may play an important role in local maintenance of the disease. Studies on the epidemiology of CWD have led to the development of models to help explain the history of CWD and to simulate future impacts on deer and elk populations. Diagnostic tests have been improved, allowing diagnosis early in the incubation period, long before the appearance of clinical disease. Surveillance techniques and programmes have been developed and instituted by wildlife management agencies for free-ranging deer and elk and by state and federal agricultural agencies for privately-owned elk. During the 1990s, perceptions of TSEs have altered dramatically; perhaps most remarkably, the goal of global eradication of all prion diseases is now being discussed.