Dear Colleagues:

This is an important review and update on the health impacts of WASH:

Link to full-text - Impact of Drinking Water, Sanitation and Hand Washing with Soap on Childhood Diarrhoeal Disease: Updated Meta-Analysis and –Regression. Tropical Medicine and International Health, 14 March 2018.

Authors: Jennyfer Wolf, Paul R. Hunter, Matthew C. Freeman, Oliver Cumming, Thomas Clasen, Jamie Bartram, Julian P. T. Higgins, Richard Johnston, Kate Medlicott, Sophie Boisson, Annette Prüss-Us

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/tmi.13051

Objectives - Safe drinking water, sanitation and hygiene are protective against diarrhoeal disease; a leading cause of child mortality. The main objective was an updated assessment of the impact of unsafe water, sanitation and hygiene (WaSH) on childhood diarrhoeal disease.

Methods - We undertook a systematic review of articles published between 1970 and February 2016. Study results were combined and analysed using meta-analysis and meta-regression.

Results - A total of 135 studies met the inclusion criteria. Several water, sanitation and hygiene interventions were associated with lower risk of diarrhoeal morbidity.

- Point-of-use filter interventions with safe storage reduced diarrhoea risk by 61% (RR=0.39; 95% CI: 0.32, 0.48);
- piped water to premises of higher quality and continuous availability by 75% and 36% (RR=0.25 (0.09, 0.67) and 0.64 (0.42, 0.98)), respectively compared to a baseline of unimproved drinking water;
- sanitation interventions by 25% (RR=0.75 (0.63, 0.88)) with evidence for greater reductions when high sanitation coverage is reached; and interventions promoting handwashing with soap by 30% (RR=0.70 (0.64, 0.77)) versus no intervention.

Results of the analysis of sanitation and hygiene interventions are sensitive to certain differences in study methods and conditions. Correcting for non-blinding would reduce the associations with diarrhoea to some extent.

Conclusions - Though evidence is limited, results suggest that household connections of water supply and higher levels of community coverage for sanitation appear particularly impactful which is in line with targets of the Sustainable Development Goals.