Outbreak of Acute Enteric Disease Associated With Drinking Water in a Rural Area of Kazakhstan: A Matched Case-control Study
- Occupational and environmental health
- Water or foodborne
Background: Surveillance showed an uptick in enteric disease of unknown etiology in the village of Beskol (12,000 inhabitants) in North Kazakhstan. We conducted an outbreak investigation to identify risks and sources.
Methods: Suspected cases were acutely ill residents presenting for medical treatment for diarrhea, fever (>37.5 °C), vomiting, or weakness from May 14–June 15, 2021. Controls were residents matched by age ±2 years at a ratio of 2 controls for every case. Cases and controls were interviewed June 3–13, using structured questionnaires. We abstracted clinical data from medical records. We mapped cases in QGIS and computed odds ratios (OR) and 95% confidence interval (CI) using conditional multivariable logistic regression.
Results: We identified 154 suspected cases of acute enteric disease; 46% were <7 years old. Most commonly reported symptoms were diarrhea, fever, vomiting, weakness, and decreased appetite. A total of 107 (70%) cases and 219 controls agreed to participate. Among cases, 74% drank unboiled tap water compared to 18% of controls. This was the only risk factor significantly associated with disease (OR=19; 95% CI=10–36). Drinking water from a dispenser or carbonated drinks was significantly protective than persons who did not drink from these sources. The city has 2 water supply networks; cases were clustered (107 cases in 70 foci) in one. The investigation found that monitoring of quality and safety of water according to national regulations had not been conducted since 2018. No fatalities occurred, and no associated cases were reported after our investigation.
Conclusions: Results suggest that untreated tap water was the probable source of the outbreak. The water supply had been cleaned and disinfected twice by the facility 2 days before our investigation began. Recommendations were made for regular monitoring of water supply facilities with rapid public notification when issues are detected to reduce likelihood of future drinking water associated outbreaks.
Methods: Suspected cases were acutely ill residents presenting for medical treatment for diarrhea, fever (>37.5 °C), vomiting, or weakness from May 14–June 15, 2021. Controls were residents matched by age ±2 years at a ratio of 2 controls for every case. Cases and controls were interviewed June 3–13, using structured questionnaires. We abstracted clinical data from medical records. We mapped cases in QGIS and computed odds ratios (OR) and 95% confidence interval (CI) using conditional multivariable logistic regression.
Results: We identified 154 suspected cases of acute enteric disease; 46% were <7 years old. Most commonly reported symptoms were diarrhea, fever, vomiting, weakness, and decreased appetite. A total of 107 (70%) cases and 219 controls agreed to participate. Among cases, 74% drank unboiled tap water compared to 18% of controls. This was the only risk factor significantly associated with disease (OR=19; 95% CI=10–36). Drinking water from a dispenser or carbonated drinks was significantly protective than persons who did not drink from these sources. The city has 2 water supply networks; cases were clustered (107 cases in 70 foci) in one. The investigation found that monitoring of quality and safety of water according to national regulations had not been conducted since 2018. No fatalities occurred, and no associated cases were reported after our investigation.
Conclusions: Results suggest that untreated tap water was the probable source of the outbreak. The water supply had been cleaned and disinfected twice by the facility 2 days before our investigation began. Recommendations were made for regular monitoring of water supply facilities with rapid public notification when issues are detected to reduce likelihood of future drinking water associated outbreaks.