Moving Towards Transformational WASH: Authors' Response

The authors agree with Karen Levy and Joseph Eisenberg that observational studies of water, sanitation, and hygiene (WASH) interventions with carefully designed counterfactuals can play a valuable role in generating evidence on effectiveness, particularly in urban settings. Randomised controlled trials for community-level WASH infrastructure interventions are not always feasible in urban settings, because of the political and logistical constraints of defining treatment and control groups; strong observational designs could help fill the gap. With increasing urbanisation in Asia and Africa, WASH intervention studies in low-income urban communities will be crucial for informing strategies to meet Sustainable Development Goal (SDG) target 6.1: to achieve universal and equitable access to safe and affordable drinking water for all.