A stepped wedge, cluster-randomized trial of a household UV-disinfection and safe storage drinking water intervention in rural Baja California Sur, Mexico

Abstract

In collaboration with a local non-profit organization, this study evaluated the expansion of a program that promoted and installed Mesita Azul, an ultraviolet-disinfection system designed to treat household drinking water in rural Mexico. We conducted a 15-month, cluster-randomized stepped wedge trial by randomizing the order in which 24 communities (444 households) received the intervention. We measured primary outcomes (water contamination and diarrhea) during seven household visits. The intervention increased the percentage of households with access to treated and safely stored drinking water (23-62%), and reduced the percentage of households with Escherichia coli contaminated drinking water (risk difference (RD): -19% [95% CI: -27%, -14%]). No significant reduction in diarrhea was observed (RD: -0.1% [95% CI: -1.1%, 0.9%]). We conclude that household water quality improvements measured in this study justify future promotion of the Mesita Azul, and that future studies to measure its health impact would be valuable if conducted in populations with higher diarrhea prevalence.

Figure 1.

Stepped Wedge Schematic for the Mesita Azul Intervention Study. Twenty-four clusters were enrolled at baseline (t = 0) and randomly ordered. All communities started in the control group (white squares). The first four randomly ordered communities (crossover group 1) received the intervention (gray squares) at Step-1 (t = 1). The next four communities (crossover group 2) received the intervention in Step-2, and so on. Within each crossover group two communities were randomized to the Basic Program (dark gray squares) and two to the Enhanced Program (light gray squares). Once a community crossed-over it remained in the intervention group for the remainder of the study. Randomized rollout balances covariates between control- (white squares) and intervention- (all gray squares) periods and creates two comparison groups.

Figure 2.

Flow Diagram of the Mesita Azul Trail Study Population. After baseline, four households (HHs) crossed over to the intervention in each step.

Figure 3.

Percent of households with contaminated drinking water by treatment arm and step (black triangles: intervention households; open circles: control households; black bars: 95% confidence intervals).

Figure 4.

Seven-day prevalence of diarrhea by treatment arm and step (black triangles: intervention households; open circles: control households; black bars: 95% confidence intervals).