During 2009, more than 50 million people swam during an estimated 300 million visits to recreational waters in the U.S. (U.S. Census Bureau, 2011). Included among recreational waters are hot tubs, swimming pools, lakes, oceans, and rivers. Among potential risks for recreational swimming is waterborne illness resulting from ingestion of contaminated water. Diarrhea, the most common manifestation of waterborne illness, results when a person ingests water contaminated with enteric pathogens, including Cryptosporidium, Giardia, Shigella, norovirus, and E. coli O157:H7 (Hlavsa et al., 2011).
Despite being among the most common enteric pathogens, nontyphoidal Salmonella is rarely identified as the source of waterborne illness (World Health Organization, 2008). During June 2014, the Tennessee Department of Health (TDH) investigated a salmonellosis outbreak associated
with a single splash pad. Splash pads, which are not regulated in Tennessee, are any fountain or water spray device intended for or accessible to recreational use (see photo on page 9). A limited number of outbreaks associated with splash pads have been reported, and a study of water quality was rarely included (Bancroft, Keifer, & Keene, 2012; Eisenstein, Bodager, & Ginzl, 2008; Kirian, Meregillano, Gennette, & Weintraub, 2008; Nett et al., 2010). We investigated the outbreak of salmonellosis and then conducted a statewide survey of splash pads to learn more about their water quality and observe patron behaviors that might increase the risk for infection.
During June 2014, routine disease surveillance and patient interviews conducted by TDH identified an outbreak of five Salmonella Newport infections among patrons of a single splash pad. Standard outbreak investigation methods were used, including case finding from local healthcare providers, patient interviewing, and laboratory isolation and subtyping by pulsed-field gel electrophoresis (PFGE). A case-control study was performed to identify exposures associated with Salmonella infection among patrons of the implicated splash pad.
Cases were defined as either confirmed (a person who developed diarrhea, defined as [greater than or equal to] 3 loose stools during 24 hours, within 16 days of visiting the splash pad, and with laboratory confirmation of Salmonella Newport) or probable (a person who developed diarrhea within 16 days of visiting the splash pad without laboratory confirmation). The 16-day incubation period for Salmonella was used because the ingestion dose was likely low because of the dilution effect of the splash pad water (Heymann, 2004). We attempted to match three control subjects per case-patient, stratified by age group. Control subjects were age matched to case-patients and had visited the splash pad in the previous 30 days. Internet directories were used to identify households in the community near the splash pad and telephone calls were made to enroll control subjects. TDH staff visited the splash pad to enroll additional patrons as control subjects via in-person contact. After the outbreak was identified, a chlorine reading was taken and TDH staff reviewed the maintenance logs during the initial visit. During a subsequent visit, an environmental assessment and water samples were taken.
Splash Pad Survey
In response to the waterborne Salmonella outbreak, we conducted a survey during August 2014 of all identified splash pads in Tennessee to learn about their operating characteristics. A comprehensive list of splash pads was unavailable, so we identified sites by searching the Internet for terms commonly used to name or describe them (e.g., splash pads, interactive fountains, or aquatic playgrounds); reviewing splash pad manufacturer web pages for past, current, and future projects; and reviewing award announcements from the Tennessee Department of Environment and Conservation's parks and recreation grants. Splash pad operators were requested to participate in the survey during an unannounced site visit. Participating site operators were asked questions addressing water recirculation...