Evaluation of an Emergency Water Tank Monitoring Program Implemented During Cholera Outbreak in Lusaka, Zambia (2017-2018).

Access to safely managed drinking water is critical for preventing the spread of cholera. In October 2017, a cholera outbreak was declared in Lusaka, Zambia. As a part of response efforts, emergency water tanks were installed across Lusaka to supply treated water to community members. An emergency water tank monitoring program was implemented for more than 4 months to routinely assess tank conditions and measure free chlorine residual (FCR) levels in the tanks. More than 9,700 tank visits were conducted across 281 tanks. Tanks were empty at 23% of visits, leaking at 14% of visits, and had broken or missing parts at 20% of visits; these conditions were absent at 61% of visits. A key finding was that 87% (n = 6,455) of FCR measurements met the target level (FCR ≥1.0 mg/L); tanks with FCR <1.0 mg/L were reported in real time to water utility and public health officials for corrective action. A survival analysis model was developed to assess the associations between low FCR events (<1.0 mg/L) and broken or missing parts and empty tanks. A significant increase in the probability of a low FCR event (hazard ratio [HR] = 1.52; 95% CI: 1.19-1.95) and tank emptiness (HR = 1.39; 95% CI: 1.08-1.79) was found after the observations of broken or missing parts (the median time to event was 3 days). A significant decrease in low FCR levels (HR = 0.83; 95% CI: 0.70-0.98) was also found after leakage. These results highlight the importance of systematic tank monitoring to ensure that treated water reaches community members during cholera outbreaks.