Water, sanitation, and hygiene interventions in outbreak response: a synthesis of evidence

Water, sanitation, and hygiene (WASH) interventions are key to reducing the burden of disease associated with outbreaks, and are commonly implemented in emergency response. However, there is a lack of summarized evidence on the efficacy and effectiveness of these interventions. We conducted a systematic review of published and grey literature by developing theory of change models, developing inclusion criteria, conducting the search, selecting evaluations for inclusion, assessing the quality of the evidence, and analysing the included evaluations. Overall, 15,026 documents were identified and 51 evaluations from 47 studies met inclusion criteria. Interventions from 19 countries were included, primarily in response to cholera (86 per cent). Most included evaluations (70 per cent) were at high risk of bias and nearly half were from grey literature (49 per cent). We found that WASH interventions consistently reduced both the risk of disease and the risk of transmission in outbreak contexts; however, programm...