Case–control studies are conducted to identify cholera transmission routes, and Water, sanitation, and hygiene (WASH) exposures can facilitate or interrupt cholera transmission. Up until now there had been no systematic analysis of the association between WASH exposures and cholera from case–control studies. Seeing this gap, researchers from Tufts University Civil and Environmental Engineering Department, Medford, Massachusetts undertook a systematic review. The review describes the theory of risk and protection, developes inclusion criteria, searches and selects studies, assesses quality of evidence, and summarises associations between cholera and seven predicted WASH protective factors and eight predicted WASH risk factors using meta-analysis and sensitivity analysis. Overall, 47 articles describing 51 individual studies from 30 countries met the inclusion criteria.

In summary, the review shows that improved hygiene demonstrated the greatest reduction in the odds of cholera, whereas open defecation most increased the odds of cholera. Among the predicted protective factors, neither improved water source nor improved sanitation was associated with cholera.

(Article published in American Journal of Tropical Medicine and Hygiene, August 2, 2018.)