Surveillance of smallpox.

An intensified global smallpox eradication programme was started by the World Health Organization in 1967. This paper describes the basic techniques employed and the experiences involved in implementing the procedures. Surveillance schemes have varied considerably in detail from country to country according to different health structures, and the emphasis is therefore placed on the more generally used approaches. Finally, important principles in the implementation of the smallpox surveillance programme are considered in relation to the development of such programmes for other communicable diseases.