Association between Rainfall and Pediatric Emergency Department Visits for Acute Gastrointestinal Illness

Abstract

BackgroundMicrobial water contamination after periods of heavy rainfall is well described, but its link to acute gastrointestinal illness (AGI) in children is not well known.ObjectivesWe hypothesize an association between rainfall and pediatric emergency department (ED) visits for AGI that may represent an unrecognized, endemic burden of pediatric disease in a major U.S. metropolitan area served by municipal drinking water systems.MethodsWe conducted a retrospective time series analysis of visits to the Children’s Hospital of Wisconsin ED in Wauwatosa, Wisconsin. Daily visit totals of discharge International Classification of Diseases, 9th Revision codes of gastroenteritis or diarrhea were collected along with daily rainfall totals during the study period from 2002 to 2007. We used an autoregressive moving average model, adjusting for confounding variables such as sewage release events and season, to look for an association between daily visits and rainfall after a lag of 1–7 days.ResultsA total of 17,357 AGI visits were identified (mean daily total, 7.9; range, 0–56). Any rainfall 4 days prior was significantly associated with an 11% increase in AGI visits. Expected seasonal effects were also seen, with increased AGI visits in winter months.ConclusionsWe observed a significant association between rainfall and pediatric ED visits for AGI, suggesting a waterborne component of disease transmission in this population. The observed increase in ED visits for AGI occurred in the absence of any disease outbreaks reported to public health officials in our region, suggesting that rainfall-associated illness may be underestimated. Further study is warranted to better address this association.

Impact of Rainfall on Diarrheal Disease Risk Associated with Unimproved Water and Sanitation

“…The variability in pathogen prevalence between regions may also explain the wide range of lag periods associated with diarrhea across studies. [10][11][12][13][14] At our study site, a 5-week rainfall period was most strongly correlated with diarrhea. This correlation may be influenced by the environmental persistence of rotavirus and Giardia cysts in water, sewage, and soil for up to several weeks.…”

“…Our finding that extreme rainfall was protective for diarrhea is consistent with some studies 10 and inconsistent with others. 11,13,14,26 The reasons for this discrepancy in the literature may be because of the fact that the context in each study is different (i.e., factors that are protective under some circumstances are often a risk under other circumstances). With regards to the relationship between rainfall and diarrhea, the distribution of improved water and sanitation facilities, the patterns of rainfall, and the distribution of pathogens causing diarrhea may be important defining contexts to consider.…”

“…It may be for these reasons that the relationship between rainfall and diarrhea remains unclear. Recent studies have shown positive, [10][11][12]41 negative, 10,41 and threshold-type associations between rainfall and diarrheal disease. 13,14 In these studies, rainfall indicators included total, average, or number of extreme rainfall events defined by some threshold over a period of time (referred to as a lag period).…”

Drinking Water Systems, Hydrology, and Childhood Gastrointestinal Illness in Central and Northern Wisconsin

“…On average, rainy days recorded 11% more emergency department GI visits than nonrainy days in Milwaukee. 15 Very high (> 90th percentile) water volumes (combined effect of snowmelt and rainfall) increased weekly GI clinic visits 30% compared with moderate or dry weeks in an Inuit community. 40 In Northwestern England, wet conditions in the previous week (75th percentile) increased weekly cryptosporidiosis rates 27%.…”

“…13,14 In fact, communities that are primarily served by minimally treated drinking water may record elevated GI incidence during these hydrologic events. 15,16 Snowmelt or extreme precipitation may cause combined sewer overflow events, which also increase GI rates. 17 Assuming drinking water is the primary exposure route to waterborne pathogens, GI rates are likely insensitive to hydrologic changes when drinking water infrastructure and treatments function properly.…”