In early 2013 WHO convened an expert group of scientists from 14 collaborating research institutions to update theassessment of the burden of diarrhoeal disease from inadequate water sanitation and hygiene (WASH) and to reassessthe effectiveness of WASH interventions. This group considered evolving and alternative methods for assessing theburden of disease and agreed on a rigorous new approach using meta-regression. In deriving the new figures theexperts incorporated the latest data on use of improved water and sanitation with minor adjustments and drew uponthe results from two new global