Citation:

Lin, C., Tim Wade, AND E. Hilborn. Flooding and intestinal illness due to Clostridium difficile infection: a case-crossover analysis of Massachusetts data, 2003-2007. Presented at Next Generation Climate Data Products Workshop, Boulder, CO, July 15 - 19, 2013.

Impact/Purpose:

Evaluate the associations between C. diff infections and flooding

Description:

Background. Climate change has contributed to a rise in extreme weather events, including heavier rainfalls. Floods can cause water bodies to overflow, damage water treatment and drinking water infrastructure, overwhelm sewage treatment facilities, and result in discharges of untreated sewage that introduce human microbial pathogens to surface waters. Consequently, floods can facilitate the contamination of recreational or drinking water sources, food, property, etc. Such contamination can increase the fecal-oral transmission of acute gastrointestinal illness. Clostridium difficile is a bacterium that can cause acute gastrointestinal symptoms. It often affects older adults who are hospitalized and receiving antibiotics. In recent years, however, C. difficile infections have become more frequent, more severe, and more difficult to treat. Each year, tens of thousands of people in the U.S. are infected with C. difficile, including some otherwise healthy individuals who are not hospitalized or taking antibiotics. Studies have demonstrated the potential for water to be a source of C. difficile infection and the possibility of contamination by C. difficile in drinking water distribution systems. Few studies have quantified the health risks associated with flood events in the U.S. Preliminary studies have suggested an increase in emergency room visits for any acute gastrointestinal illness following flood events. We report the first evaluation of community-acquired C. difficile infections following flooding. Methods. A case-crossover design was used to assess the impact of flooding on emergency room visits for gastrointestinal illness due to C. difficile infection in Massachusetts. Information on flood events in Massachusetts was obtained from the NOAA Climatic Data Center Storm Events Database. Floods were classified by town or county of impact. Emergency room visit data were obtained for the years 2003-2007 and illness classified by diagnostic code. Four control periods, matched by date and town or county of residence, were selected per case for each of the remaining years in the study period. Matching by date was used to control for the distinct seasonal patterns in both acute gastrointestinal illness and precipitation. The risk period was defined as the period between the date the flood started and 10, 20, or 30 days beyond the end of the flood. These extended risk periods were considered to account for the delay between the flood event, contamination of the environment, exposure, extended survival of spores (up to 70 days), and the incubation period of the infection (3 days). Cases and controls were exposed if a flood occurred in the town or county of residence during the defined risk period, and unexposed if there was no flood event. Data were analyzed using conditional logistic regression. Results. During the years 2003 through 2007, there were 160 flood events in Massachusetts recorded in the NOAA database. Over the five year period, there were 1,083 diagnoses of intestinal infection due to C. difficile. Among adults between the ages 19 and 64 years, emergency room visits for intestinal infection due to C. difficile were elevated in the 10, 20, and 30 days following a flood with odds ratios (95% confidence intervals) of 1.56 (0.89, 2.75), 1.83 (1.19, 2.80), and 1.67 (1.15, 2.45), respectively. Conclusion. Emergency room visits for intestinal infection due to C. difficile increased following flood events in Massachusetts during the years 2003-2007. Further investigation is needed to confirm this finding and to explore the most relevant lag period. Future work should also consider details regarding the specific nature and severity of the flood events. This abstract does not necessarily reflect EPA policy.

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