Water use and acute diarrhoeal illness in children in a United States metropolitan area.

We examined the association between water exposures and acute diarrhoeal illness (ADI) in children under non-outbreak conditions in a major US metropolitan area. We used a nested case-control study of children seen in an urban/suburban emergency department. Cases were those seen for a complaint of diarrhoea, while controls were age-matched children with a non-gastrointestinal complaint. Parents of subjects completed a validated water-use survey. Stratum-specific adjusted odds ratios (aOR) were calculated for the three main water effects: water source [surface vs. ground (well)], drinking-water type (tap vs. bottled), and use of water filters. Of 2472 subjects, 45% drank mostly or only bottled water. Well-water use was associated with increased odds of ADI compared to surface water [aOR 1·38, 95% confidence interval (CI) 1·01-1·87]. Use of bottled water did not affect the odds of ADI in well-water users, but increased the odds of ADI for surface-water users (aOR 1·27, 95% CI 1·02-1·57). We conclude that well-water use and bottled-water use are associated with increased odds of ADI in children.