Improved water supply infrastructure to reduce acute diarrhoeal diseases and cholera in Uvira, Democratic Republic of the Congo: Results and lessons learned from a pragmatic trial

Background Safely managed drinking water is critical to prevent diarrhoeal diseases, including cholera, but evidence on the effectiveness of piped water supply in reducing these diseases in low-income and complex emergency settings remains scarce.Methods We conducted a trial of water supply infrastructure improvements in Uvira (DRC). Our primary objective was to estimate the relationship between a composite index of water service quality and the monthly number of suspected cholera cases admitted to treatment facilities and, as a secondary analysis, the number of cases confirmed by rapid diagnostic tests. Other exposures included the quantity of supplied water and service continuity. We used Poisson generalised linear models with generalised estimating equations to estimate incidence rate ratios.Findings Associations between suspected cholera incidence and water service quality (RR 0<middle dot>86, 95% CI 0<middle dot>73-1<middle dot>01), quantity (RR 0<middle dot>80, 95% CI 0<middle dot>62-1<middle dot>02) and continuity (RR 0<middle dot>81, 95% CI 0<middle dot>77-0<middle dot>86) were estimated. The magnitudes of the associations were similar between confirmed cholera incidence and water service quality (RR 0<middle dot>84, 95% CI 0<middle dot>73-0<middle dot>97), quantity (RR 0<middle dot>76, 95% CI 0<middle dot>61-0<middle dot>94) and continuity (RR 0<middle dot>75, 95% CI 0<middle dot>69-0<middle dot>81). These results suggest that an additional 5 L/user/day or 1.2 hour per day of water production could reduce confirmed cholera by 24% (95% CI 6-39%) and 25% (95% CI 19-31%), respectively.Interpretation Ensuring a sufficient and continuous piped water supply may substantially reduce the burden of endemic cholera and diarrhoeal diseases but evaluating this rigorously is challenging. Pragmatic strategies are needed for public health research on complex interventions in protracted emergency settings.Trial registration The trial is registered in ClinicalTrials.gov ID NCT02928341. https://classic.clinicaltrials.gov/ct2/show/NCT02928341. Diarrhoeal diseases including cholera remain a leading cause of mortality and morbidity, especially in areas with limited access to safe water, sanitation and hygiene (WASH). However, evidence for the effect of piped water supply in reducing diarrhoeal diseases and cholera in complex emergency settings remains scarce. We evaluated a large-scale infrastructure programme to improve and expand the piped drinking water supply service in the town of Uvira (South Kivu, Democratic Republic of the Congo), an area with a high burden of cholera and diarrhoeal diseases. We used five years of data from clinical surveillance and systematic cholera confirmation by rapid diagnostic tests in order to estimate associations between water supply infrastructure interventions and the incidence of diarrhoeal diseases and cholera. Our findings are consistent with existing evidence that a high-quality (or "safely managed") water service can be effective in reducing the burden of diarrhoeal diseases and cholera in low-income urban settings. Beyond overall service quality, the quantity of water supplied to the household and the continuity of the drinking water supply were both associated with a reduced risk of cholera.