The media has been awash in stories about an new CDC study that found the DNA of E. coli in Atlanta area pools like it was a surprise.  I guess they forgot the White Water Water Park E. coli Outbreak.

In June of 1998, Georgia health officials were notified that a number of children had become ill with E. coli O157:H7 infections and were hospitalized in Atlanta-area hospitals.  Public health investigators interviewed victims’ families and learned that all had become ill after visiting the White Water Water Park.  The Georgia Department of Health eliminated other possible sources of exposure, such as contaminated food, and determined that contact with and ingestion of pool water infected most of the primary cases.

Twenty-six culture-confirmed E. coli cases were identified, and while health officials hypothesized that the outbreak was considerably larger, the outbreak size was never known due to under-reporting of illnesses.  Forty percent of children under five years of age with recognized E. coli infections were diagnosed with hemolytic uremic syndrome.  One young two-year-old girl died.

Cases appeared on four different days, and all cases occurred within a period of eight days.  The largest number of infections took place on June 12, and the second-largest number of infections occurred on June 17, which led health officials to believe the E. coli was re-introduced to the park environment on June 17.  The PFGE pattern, or “genetic fingerprint” of the strain of bacteria isolated from ill individuals was indistinguishable between visitors to the park on June 11 and 12 and June 17.

Investigators considered three potential causes of contamination in their outbreak analysis:  repeat contamination of the park by an E. coli-infected person, persistence of bacteria in pool water overnight due to low chlorine levels, or persistence of bacteria in the pool environment but not in the water.  Low chlorine levels in the suspect pools were detected on all days of exposure, and it was never determined whether one of the pools had chlorine in it at the time when the exposures occurred.

As the CDC said in “Microbes in Pool Filter Backwash as Evidence of the Need for Improved Swimmer Hygiene — Metro-Atlanta, Georgia, 2012:”

Filters physically remove contaminants, including microbes, from water in treated recreational water venues, such as pools. Because contaminants accumulate in filters, filter concentrates typically have a higher density of contamination than pool water. During the 2012 summer swimming season, filter concentrate samples were collected at metro-Atlanta public pools. Quantitative polymerase chain reaction (qPCR) assays were conducted to detect microbial nucleic acid. Pseudomonas aeruginosa was detected in 95 (59%) of 161 samples; detection indicates contamination from the environment (e.g., dirt), swimmers, or fomites (e.g., kickboards). P. aeruginosa detection underscores the need for vigilant pool cleaning, scrubbing, and water quality maintenance (e.g., disinfectant level and pH) to ensure that concentrations do not reach levels that negatively impact swimmer health. Escherichia coli, a fecal indicator, was detected in 93 (58%) samples; detection signifies that swimmers introduced fecal material into pool water. Fecal material can be introduced when it washes off of swimmers’ bodies or through a formed or diarrheal fecal incident in the water. The risk for pathogen transmission increases if swimmers introduce diarrheal feces. Although this study focused on microbial DNA in filters (not on illnesses), these findings indicate the need for swimmers to help prevent introduction of pathogens (e.g., taking a pre-swim shower and not swimming when ill with diarrhea), aquatics staff to maintain disinfectant level and pH according to public health standards to inactivate pathogens, and state and local environmental health specialists to enforce such standards.