FIGURE 3—

Association between childhood gastrointestinal illness and weekly summer/fall hydrologic conditions adjusted for seasonality and secular trends in untreated municipal areas: Marshfield Epidemiologic Study Area, Central and Northern Wisconsin, 1991–2010.

Note. Precipitation is positively and nonlinearly associated with gastrointestinal illness. The solid line represents the estimate spline curve, and the dashed lines represent the 95% confidence intervals. The density of hash marks along the x-axis indicates the frequency of weeks with each precipitation observation.