摘要：Objectives. To provide summary estimates of gastroenteritis risks and illness burden associated with recreational water exposure and determine whether children have higher risks and burden. Methods. We combined individual participant data from 13 prospective cohorts at marine and freshwater beaches throughout the United States (n = 84 411). We measured incident outcomes within 10 days of exposure: diarrhea, gastrointestinal illness, missed daily activity (work, school, vacation), and medical visits. We estimated the relationship between outcomes and 2 exposures: body immersion swimming and Enterococcus spp. fecal indicator bacteria levels in the water. We also estimated the population-attributable risk associated with these exposures. Results. Water exposure accounted for 21% of diarrhea episodes and 9% of missed daily activities but was unassociated with gastroenteritis leading to medical consultation. Children aged 0 to 4 and 5 to 10 years had the most water exposure, exhibited stronger associations between levels of water quality and illness, and accounted for the largest attributable illness burden. Conclusions. The higher gastroenteritis risk and associated burden in young children presents important new information to inform future recreational water quality guidelines designed to protect public health. Each year there are an estimated 2.2 billion tourist day visits to freshwater and marine beaches in the United States. 1 To minimize illness associated with swimming in contaminated water, the US Environmental Protection Agency (EPA) and the World Health Organization publish beach-monitoring guidelines on the basis of Enterococcus spp. fecal indicator bacteria levels. 2,3 Elevated Enterococcus levels in recreational waters can indicate potential contamination with fecal waste from sewage or other sources and can be associated with pathogens such as norovirus, Campylobacter spp., Salmonella spp., Cryptosporidium spp., and Giardia spp. Recent waterbody closures at Brazilian Olympic venues 4 and Waikiki beach, Hawaii 5 illustrate recreational water contamination’s public health and economic reach. Several cohort studies and randomized trials have measured swimming-related health risks and risks associated with exposure to waters containing elevated fecal indicator bacteria levels, 6–17 but individual studies are usually too small to estimate the public health burden associated with water exposure with respect to missed daily activities (work, school, vacation) or medical visits and hospitalizations that result from gastroenteritis. Moreover, individual studies have not typically enrolled enough swimmers to estimate risks separately for children. Children are hypothesized to have a higher risk of swimming-related gastroenteritis than are adults because they spend more time in the water, are more likely to swallow water (the primary mechanism of pathogen exposure), and have less developed immune systems. 8,18–20 The EPA and the World Health Organization acknowledge that children could be at higher risk than is the general population but note that evidence for higher risks among children has been inconclusive when viewed across diverse environmental settings such as marine water and freshwater. 2,21 We conducted a pooled analysis of 13 prospective cohorts in the United States (84 411 participants). 7–14 We coordinated studies to ensure similar designs and measurement methods. This approach enabled us to calculate summary estimates for gastroenteritis risk and related medical and daily activity impacts associated with recreational water exposure and Enterococcus levels; it also enabled us to report for the first time, to our knowledge, separate estimates for children aged 0 to 4 and 5 to 10 years. We had 3 objectives: (1) estimate the risk of diarrhea among beachgoers associated with recreational water exposure, (2) estimate the risk of diarrhea among swimmers associated with Enterococcus levels measured in the water, and (3) estimate the illness burden attributable to recreational water exposure and exposure above regulatory guidelines for the following outcomes: diarrhea, gastrointestinal illness, missed daily activities (work, school, vacation) owing to gastrointestinal illness, and medical consultations owing to gastrointestinal illness.
