4 1 2 Defining the current situation - epidemiology 3 4 5 6 7

The first step in any economic appraisal or evaluation is to understand the underlying problem being addressed (see Chapter 1). Clearly such analysis of drinking-water interventions will have a strong public health element. This chapter introduces the reader to the role that epidemiology has in determining the burden of disease in a community that may be attributable to lack of access to safe drinking-water and/or adequate sanitation. In order to determine how important such an issue may be one has to ask three questions: What is the burden of disease in the target group? Burden of disease is a function of the incidence and severity of the disease. What proportion of the burden of disease is due to deficiencies in access to drinking-water to be remedied by the intervention? Are there any spin-off livelihood responses that would result from the outcomes of the intervention?