Interactive fountains (also known as spray parks and pads) feature water discharged from jets, sprinklers, cannons, spray nozzles and sculptures, which are mounted on accessible, ground-level play platforms.  Children can manipulate varieties of valve caps and nozzles to control how they are sprayed or doused with water. These venues provide accessible and free entertainment with their very shallow or ‘zero-depth’ environments; drowning potential is extremely low.  They require relatively lower construction costs and far lower operating costs than outdoor swimming pools–in some municipalities, public swimming pools account for the highest operating cost of any recreational or cultural facility.  It is not surprising, then, that interactive fountains are appearing in parks everywhere, while many city pools are closing.

Cryptosporidium parvum oocysts
Cryptosporidium parvum oocysts/CDC/ DPDx

Interactive fountains must draw their water from one of two sources: continuous flow from a jurisdiction’s treated drinking water system or a self-contained recirculating treatment system.  Continuous flow systems require relatively less upfront construction costs, but many operators prefer to build self-contained systems—these collect water from the play area into underground storage reservoirs for filtering, chlorination and re-use. Because water from re-circulating systems is not lost to sewerage, water wastage and operating costs are far lower.  Within re-circulating systems, storage tanks can hold four to five times their flow rate, so their valves can stream unrestricted for maximum soaking effect and at a warmer ambient temperature, without the need for mechanical heat—a preferred experience for bathers. In theory, with the proper chlorination and filtration equipment in place, a re-circulating system should be nearly as hygienic as a continuous flow system.

Unfortunately, interactive fountains with recirculating systems have been implicated as the source of outbreaks since 1997 of recreational water-associated diarrheal disease caused by a protozoan, Cryptosporidium. This parasite infects over 45 species of animals, including birds, rodents, dogs, cats, while two of its species are associated most often with human infection, C. parvum and C. hominis.  Symptoms, which include malaise, profuse and watery diarrhea, nausea, vomiting, fever and severe cramping, typically wax and wane for 30 days before self-resolving, but many cases are asymptomatic.  Infection in immunocompromised persons can manifest like cholera, become debilitating, lead to severe weight loss and even death. This organism produces oocysts, its infectious stage, which are shed by the millions in a single bowel movement. Transmission occurs via ingestion of fecally-contaminated water or food; since only as few as ten oocysts are necessary to initiate infection, a mouthful of water will suffice.

Two outbreaks stand out as examples that the number of cases produced from a single interactive fountain can be substantial: one in Florida in 1999 in which 44% of the estimated 4,800 persons became ill with diarrheal disease (from Cryptosporidium and Shigella), and another in 2005 at Seneca Lake State Park in New York State where 4,000 attendees suffered from infection with Cryptosporidium.  The CDC reported on the most recent data available regarding recreational water-associated disease: in 2011-2012 ninety outbreaks occurred across 32 states and affected 1,788 persons; of these, 77% were associated with treated recreational water, and over half of these were caused by infection with Cryptosporidium.  The frequency of new cases of infection from this parasite remains elevated since 2007 across the United States.  Young children (aged 1-9) have been the most affected, and cases have spiked typically in the months of July and August.

There is no uniform regulation of recreational water venues nationally in the United States; this is left to local authorities. Because interactive fountains do not fall usually under the classification of swimming pools, they are not held often to the same hygienic standards.  In some cases, they have not been regulated at all; during an outbreak in Santa Clara County (California) in 2006, environmental health officials had not been aware of the existence and location of all interactive fountains within their jurisdiction.  In more recent outbreaks in the US, splash park supervisors have not understood that their facilities pose a risk to the spread of diarrheal disease.  Some outbreaks have occurred because fountains have been improperly maintained—chlorination chemicals have been inadequately replaced.  Showering and bathroom facilities are absent at many interactive water venues.

However, even where fountains are operated under the same standards as swimming pools, often filtration and chlorination processes are not adequate to remove infective Cryptosporidium organisms from the water. Even at CDC mandated chlorine concentrations (1-3 mg/L) for recreational water venues, the parasite’s oocysts can survive for up 10 days.  The CDC advises that treatment with ultraviolet light or ozone and enhanced filtration should complement chlorination for controlling this parasite in interactive fountains.

Unhygienic activities by bathers are as much to blame for the transmission of Cryptosporidium in interactive fountains.  In one outbreak, children played in an enclosed water area that had been designed only as a decorative fountain.  Unattended accessibility for bathers presents no bar to entry for the pathogens that adhere to their feet and bodies (it has been estimated that bathers shed an average of 0.14 grams of fecal material). There are no venues that can match spray parks for their potential to accumulate and commingle the microbes of a community and aerosolize them in fine water droplets across an entire play area.  It does not matter if water comes from a fresh or re-circulated source when it deflects off an infected bather’s bottom, especially a diapered one, and splashes into the face of a child playing nearby.

Many jurisdictions have taken appropriate steps to make their interactive spray parks safer, but many still have not.  Before you let your children enjoy your local interactive fountain, you should consider a few things. Investigate the hygienic standards set by your local authorities and the record of compliance and maintenance by the managers of the spray park. Check to see if bathrooms, diaper-changing stations, showering facilities are available nearby. Inspect the venue to ensure that jets of water do not project up from the floor and that nozzles are not placed where children can sit on them. Cryptosporidium is only one reason to take extra care.

Steven Smith, M.Sc. is an Infectious diseases epidemiologist