This study, tucked away in a public health journal that most clinicians never see, is a testament to how meticulous data collection and analysis can lead to some simple conclusions. It's hard to debate the reliability of the results when the investigators go to such lengths.
Source: Arnold BF, Wade TJ, Benjamin-Chung J, et al. Acute gastroenteritis and recreational water: highest burden among young US children. Am J Public Health. 2016;106(9):1690-1697; doi:10.2105/AJPH.2016.303279. See AAP Grand Rounds commentary by Dr. Philip Rosenthal (subscription required).
The current study is really a pooling (pun intended) of data collected in 8 separate studies of swimming-associated gastroenteritis. (My pun is lamer than you think, all of these studies dealt with swimming at freshwater and marine sites, not the backyard swimming pool.) Investigators interviewed beachgoers at 9 different sites to determine demographic data, type of swimming exposure, and development of diarrhea subsequently, as well as other gastrointestinal symptoms and need for medical consultation and missed school or work days. Collectively they started with 102,903 beachgoers who agreed to be interviewed, and the data from this study was pooled from the 84,411 individuals who completed the follow-up survey.
Here's what we can take from their findings. Exposure to water (as opposed to being at the beach but not going in the water) was linked to subsequent diarrhea and missed work/school activities, but not to likelihood of seeking medical consultation. More specifically among the swimmers, those who reported immersing their bodies or heads, or swallowing water, had higher rates of diarrhea. Also, in the studies where they had data about Enterococcus concentrations in the water (a surrogate for fecal contamination), those concentrations above the Environmental Protection Agency's cutoff for safety of 35 colony-forming units per 100 mL were linked to higher diarrhea rates in swimmers than in nonswimmers, particularly in children 0 - 4 years of age. Overall, the youngest children (ages 0 - 4 years) had the highest diarrhea rates, followed by those 5 - 10 years of age and then those greater than 10 years.
I suppose we should all be a bit disgusted thinking about children swallowing fecally-contaminated water while swimming, but of course that's a fact of life. Ensuring better methods of sewage control near recreational water sites certainly could help decrease the burden of gastrointestinal disease resulting from these exposures.
I can't say the article itself is must reading from primary care providers, but if you do glance at it (access is free to all), take a moment to look at the online supplemental data, if for no other reason than to get an appreciation of the heavy lifting that goes into studies like this. Of course, you can also see if your favorite recreational water site was included in the study!
There is one take-home point for front line providers. Be sure to include recreational water exposure in your list of questions to ask when evaluating a child for diarrhea. It just might be the clue that leads to public health authorities identifying and limiting the extent of a water-borne diarrheal outbreak.
