Associations among Water, Sanitation, and Hygiene, and Food Exposures and Typhoid Fever in Case-Control Studies: A Systematic Review and Meta-Analysis

Abstract

Typhoid fever transmission occurs through ingestion of food or water contaminated with Salmonella Typhi, and case-control studies are often conducted to identify outbreak sources and transmission vehicles. However, there is no current summary of the associations among water, sanitation, and hygiene (WASH); and food exposures and typhoid from case-control studies. We conducted a systematic review and meta-analysis of case-control studies to evaluate the associations among typhoid fever and predicted WASH or food exposure risk factors (13), and protective factors (7). Overall, 19 manuscripts describing 22 case-control studies were included. Two studies were characterized as having low risk of bias, one as medium risk, and 19 as high risk. In total, nine of 13 predicted risk factors were associated with increased odds of typhoid (odds ratio [OR] = 1.4-2.4, I ² = 30.5-74.8%.), whereas five of seven predicted protective factors were associated with lower odds of typhoid (OR = 0.52-0.73, I ² = 38.7-84.3%). In five types of sensitivity analyses, two (8%) of 26 summary associations changed significance from the original analysis. Results highlight the following: the importance of household hygiene transmission pathways, the need for further research around appropriate food interventions and the risk of consuming specific foods and beverages outside the home, and the absence of any observed association between sanitation exposures and typhoid fever. We recommend that typhoid interventions focus on interrupting household transmission routes and that future studies provide more detailed information about WASH and food exposures to inform better targeted interventions.

Figure 1.

F-diagram showing pathways of fecal–oral disease and opportunities to interrupt transmission.

Figure 2.

Study selection and quality assessment flowchart.

Figure 3.

Meta-analysis of the association between water treatment and typhoid, including water treatment and no water treatment. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.

Figure 4.

Meta-analysis of the association between safe water management and typhoid. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.

Figure 5.

Meta-analysis of the association between unsafe waste management and typhoid. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.

Figure 6.

Meta-analysis of the association between hygiene and typhoid, including good hygiene and lack of hygiene. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.

Figure 7.

Meta-analysis of the association between food practices and typhoid, including protective food practices and risky food practices. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.

Figure 8.

Meta-analysis of the association between food and drink outside home and typhoid. †Study used the WHO case definition for typhoid. *Odds ratio reported from multivariate analysis.