Outbreak of acute diarrhoeal disease attributed to consumption of faecal contaminated water supplied through damaged pipelines in Thiruper, Tiruvallur district, Tamil Nadu, India, 2016

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BackgroundOn December 24, 2016, 18 Acute Diarrhoeal Disease (ADD) cases were reported in Thiruper village. We aimed to identify potential exposure and propose recommendations.MethodsWe defined a case of ADD as occurrence loose stools (≥3 episodes), December 14–30, 2016. We did door-to-door case search, calculated attack rate by age and gender, drew epidemic curve and plotted cases by residence. We conducted a matched case-control study and computed Matched Odds ratio (MOR), 95% confidence interval (95% CI) and Population Attributable Risk (PAR). We collected stool and water specimens for laboratory testing.ResultsWe identified 38 (6%) cases among 625 residents. The attack rate of ADD was higher among aged <5 years (16.5%), and female (6.8%). The outbreak lasted between 14–27 December 2016 with multiple peaks. Cases clustered in areas receiving water from damaged pipelines crossing open-defecation area. We compared 38 ADD cases with 76 age, gender and neighbourhood matched controls for different exposures. Consuming water supplied through the damaged subterranean pipeline (MOR = 3.7; 95% CI = 1.1 to 16.4; PAR = 72%) was associated with ADD. The environmental investigation pointed out potential faecal contamination of water through damaged subterranean pipelines near open-air defaecation area of village. The collected stool specimens were negative for pathogens, and water specimens tested positive for Escherichia coli.ConclusionsWe confirmed that the outbreak of ADD in Thiruper village was due to consumption of water contaminated with E. coli supplied through damaged subterranean pipelines post-cyclone. We recommended the replacement of subterranean pipelines and distribution of chlorinated water.