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Daily variability of rainfall and emergency department visits of acute gastrointestinal illness in North Carolina, 2006-2008
Citation:
Heaney, C. D., D. Richardson, A. Walker, AND J. S. JAGAI. Daily variability of rainfall and emergency department visits of acute gastrointestinal illness in North Carolina, 2006-2008. Presented at International Society for Environmental Epidemiology (ISEE) Annual Meeting, Barcelona, SPAIN, September 13 - 16, 2011.
Impact/Purpose:
We examined associations between daily average rainfall (mm) and daily counts of emergency departments visits for AGI at the county-level in NC between January 1, 2006 and December 31, 2008, controlling for time trends, seasonal patterns, and region.
Description:
Background & Aims: Projections based on climate models suggest that the frequency of extreme rainfall events will continue to rise over the next several decades. We aim to investigate the temporal relationship between daily variability of rainfall and acute gastrointestinal illness (AGI) in North Carolina (NC). Methods: County-level rainfall and emergency department visits data were obtained from the NC Climate Retrieval and Observation Network of the Southeast and NC Disease Event Tracking and Epidemiologic Collection Tool databases, respectively. We examined associations between daily average rainfall (mm) and daily counts of emergency departments visits for AGI at the county-level in NC between January 1, 2006 and December 31, 2008, controlling for time trends, seasonal patterns, and region. Using Poisson models, daily AGI rates per unit change of rainfall (mm) were calculated using lags of 0-15 days. Results: Statewide, the crude rate of AGI was 1532 per 100000 person-years (pyr) with variability by season (1857/100000 pyr in winter; 1223/100000 pyr in summer), age (8443/100000 pyr among infants ≤1 yr; 723/100000 pyr among children 10-14 yr); and region (1938/100000 pyr in the Piedmont region; 1157/100000 pyr in the Coastal region). Each additional 1-mm increase in daily average rainfall at lag day 5 was associated with one additional AGI visit per 100,000 pyrs. Conclusions: The observed temporal lag (5 days) between daily rainfall and AGI suggests waterborne transmission. Further stratified analyses, by age group and water source are needed to fully understand associations. (This abstract does not necessarily reflect EPA policy.)