Associations of Water, Sanitation, and Hygiene with Typhoid Fever in Case-Control Studies: A Systematic Review and Meta-Analysis

BackgroundTyphoid fever is a major public health issue in low- and middle-income countries. It is transmitted through fecally contaminated food or water and thus improving water, sanitation, and hygiene (WASH) is considered key to its control. We sought to quantify the association between WASH and typhoid fever. MethodsWe updated a previous review by including new findings from the literature indexed in Web of Science, Embase, and PubMed. We kept the search terms, typhoid and case-control, consistent with the previous review. We assessed the risk of bias using the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I). We categorized WASH exposures according to the WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP) classification. We conducted a Bayesian random-effects meta-analysis of odds ratios (ORs) extracted from the studies without a critical risk of bias. FindingsWe identified 25 eligible articles including 19 articles from the previous review. Pooled ORs indicated limited hygiene (OR = 2.26, 95% CrI: 1.38 to 3.64), untreated water (OR = 2.21, 95% CrI: 1.53 to 3.48) and using surface water (OR = 2.16, 95% CrI: 1.24 to 3.60) increased odds of culture-confirmed typhoid fever. On the other hand, basic hygiene (OR = 0.6, 95% CrI: 0.38 to 0.97) and treated water (OR = 0.62, 95% CrI: 0.41 to 0.89) reduced odds of culture-confirmed typhoid fever. ConclusionOur analyses updated quantitative evidence of association between WASH and typhoid fever. Our study findings will be useful to infer actionable insights on the most effective ways to control typhoid fever in low- and middle-income countries. Our analyses also offer a possibility to leverage JMP WASH data to explore potential burden of typhoid fever. Systematic review registrationPROSPERO 2021 CRD42021271881 Author SummaryTyphoid fever is a major public health issue in the low- and middle-income countries. It is transmitted through fecally contaminated food or water and thus improving water, sanitation, and hygiene (WASH) is considered key to its control. We quantified the association between WASH and typhoid fever through a systematic review of the case-control studies and meta-analyses of extracted odds ratios (ORs). We categorized WASH exposures according to the WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP). We used a Bayesian random-effects model to account for the heterogeneity of studies that were conducted at different times and places, and adjusted potential bias differently. Pooled ORs indicated that limited hygiene (OR = 2.26, 95% CrI: 1.38 to 3.64), untreated water (OR = 2.21, 95% CrI: 1.53 to 3.48) and using surface water (OR = 2.16, 95% CrI: 1.24 to 3.60) increased odds of typhoid fever. On the other hand, basic hygiene (OR = 0.6, 95% CrI: 0.38 to 0.97) and treated water (OR = 0.62, 95% CrI: 0.41 to 0.89) reduced odds of culture-confirmed typhoid fever. Our analyses updated evidence for the association between WASH and typhoid fever. The updated evidence strongly supports that improved WASH such as improved water source, water treatment, and basic hygiene will help reduce typhoid fever in low- and middle-income countries. By linking WASH exposures to new JMP WASH categories our analyses also offer a possibility to leverage JMP WASH data sets to explore potential burden of typhoid fever.