The eradication of smallpox--an overview of the past, present, and future.

The 30th anniversary of the declaration of smallpox eradication is a propitious time to look back on the evolutionary history of the program, its execution, and its legacy for the future. The eradication of history's most feared disease culminated a decade-long World Health Organization campaign which began despite skepticism and doubt and succeeded despite a never ending array of obstacles occasioned by floods, civil war, famine, and bureaucratic inertia. New concepts in public health management, surveillance, and the application of large-scale programs for vaccination were fostered and matured. A new generation of young health workers emerged who applied new approaches and experienced the gratification of public health achievement. A definitive legacy for the future was the extension of the program into an "Expanded Program on Immunization", now functioning world-wide and resulting in dramatic improvements in health through control of vaccine-preventable diseases. No less important are the growing number of multi-national programs whose foundations rest on the development of active case surveillance to measure achievement and to guide progress - poliomyelitis, measles, guinea worm, and rubella.