ABSTRACT
Surveillance is an essential part of public health practice and is vital in the control of waterborne disease. Later chapters in this section will discuss in some detail the design and management of surveillance systems for waterborne disease at local and national levels. In this chapter, we will take the opportunity to discuss some of the general principles behind the design of effective surveillance, but before progressing any further we should consider the purpose of surveillance systems. To this author, surveillance systems have value only if they lead directly or indirectly to the improvement of the health of the people surveyed.
