Splash pads really are fountains of fecal material; CDC reports 10K illnesses

There's nothing quite like a deep dive into the shallow, vomitous puddles of children's splash pads. Even toeing the edge is enough to have one longing for the unsettling warmth of a kiddie pool. But the brave souls at the Centers for Disease Control and Prevention have done it, wading into 25 years' worth of records on gastrointestinal outbreaks linked to the wellsprings of fecal pathogens. And they unsurprisingly found enough retch-inducing results to make any modern-day John Snows want to start removing some water handles.

Between 1997 and 2022, splash pads across the country were linked to at least 60 outbreaks, with the largest sickening over 2,000 water frolickers in one go. In all, the outbreaks led to at least 10,611 illnesses, 152 hospitalizations, and 99 emergency department visits. People, mostly children, were sickened with pathogens including Cryptosporidium, Camplyobacter jejuni, Giardia duodenalis, Salmonella, Shigella, and norovirus, according to the analysis, published Tuesday in the CDC's Morbidity and Mortality Weekly Report. The tallies of outbreaks and illnesses are likely undercounts, given reporting delays and missed connections.

Though previous outbreak-based studies have provided bursts of data, the new analysis is the first to provide a comprehensive catalog of all the documented outbreaks since splash pads erupted in the 1990s. Together, they provide a clear, stomach-churning explanation of how the outbreaks keep happening. Basically, small children go into the watery playgrounds while they're sick and spread their germs.

Specifically, some will vomit or poop directly into the water, while others become super spreaders simply because they haven't mastered toilet skills yet. The CDC notes that small children can have up to 10 grams of stool stuck to their butts at any point, according to some crack scientific modeling. That's about 10 standard paperclips worth of excrement. And small children tend to stand directly over jets, allowing any fecal matter stuck on their bums to wash out of their swim diapers—which do not trap poop. Some splash pads recirculate water. And among the kids who aren't standing on the jets, there are others putting their open mouths over them.

Once infectious material gets into the water, disinfection systems that aren't working properly or are inadequate can allow pathogens to gush from every nozzle. Splash pads aren't unique in having to handle sick children in poopy swim diapers—but they are unique in how they are regulated. That is, in some places, they're not regulated at all. Splash pads are designed to not have standing water, therefore reducing the risk of young children drowning. But, because they lack standing water, they are sometimes deemed exempt from local health regulations. Before 2000, only 13 states regulated splash pads. Though many states have since added regulations, some did so only after splash pad-linked outbreaks were reported.

Downpour of disease

The primary method for keeping recreational water free of infectious viruses and bacteria is chlorinating it. However, maintaining germ-killing chlorine concentration is especially difficult for splash pads because the jets and sprays aerosolize chlorine, lowering the concentration.

Still, in most splash-pad linked outbreaks, standard chlorine concentrations aren't enough anyway. The most common pathogen to cause an outbreak at splash pads is the parasite Cryptosporidium, aka Crypto. The parasite's hardy spores, called oocysts, are extremely tolerant of chlorine, surviving in water with the standard chlorine concentration (1 ppm free chlorine) for over seven days. (Other germs die in minutes.) In splash pads that might not even have that standard chlorine concentration, Crypto flourishes and can cause massive outbreaks.

In 2023, the CDC recommended new health codes that call for "secondary disinfection" methods to keep Crypto at bay, including disinfection systems using ozone or ultraviolet light. Another possible solution is to have "single-pass" splash pads that don't recirculate water.

In all, to keep splash pads from being geysers of gastrointestinal parasites and pathogens, various changes have to happen, the CDC experts say.

"Prevention of waterborne disease outbreaks at splash pads requires changes in user behavior; recreational venue code updates; and improved venue design, construction, operation, and management of facilities," they conclude. But it should all start with keeping kids from sitting on jets and drinking the water.