There is still debate and uncertainty in the literature about the health benefits of community water supply interventions. This paper reports on a changing incidence of self-reported diarrhoea associated with the implementation of two community water supplies. We conducted prospective weekly recording of diarrhoeal disease in three communities. Two of the communities were scheduled to receive an improved water supply and one was expected to continue to rely on an unimproved source during the study period. Data of self-reported diarrhoea was collected from each participating household on a weekly basis for up to 56 weeks, of which some 17 weeks were prior to implementation of the new water supply systems. Data was modelled using Generalized Estimating Equations (GEE) to account for possible clustering within households and within villages. For the two intervention communities in the study, the incidence rate ratio (IRR) for all ages after the intervention was 0.43 (95% CI 0.24-0.79) when compared to the control community (who did not receive an intervention), implying a 57% reduction of diarrhoea. Both of the new water systems were unreliable, one not operating on 4 weeks and the other on 16 weeks. The more reliable of the two intervention systems was also associated with less illness than in the least reliable system (IRR=0.41, 95% CI 0.21-0.80). We also noted anecdotal reports that during supply failures in the new systems some people were starting to use household water treatment. The implementation of improved water systems does appear to have been associated with a reduction of diarrhoeal disease in the communities. However the health impact was most obvious in the community with the more reliable system. Further research needs to be done to determine whether public health gains from community water supply interventions can be leveraged by occasional use of household water treatment (HWT) during supply failures.
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