Healthnotes Newswire (June 21, 2001)—Outbreaks of gastrointestinal illness associated with swimming pool use are on the rise, according to two new reports from the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia.^{1 2}

Most cases are caused by the protozoan parasite Cryptosporidium parvum. Between 1989 and 1998, about 10,000 reported cases of diarrhea were associated with 32 recreational waterborne disease outbreaks in various disinfected water venues in the United States. Ten of these outbreaks occurred in 1997–1998 alone. Last summer (2000), the CDC received five reports of cryptosporidium outbreaks, involving thousands of people. In addition to the reported cases, thousands more are estimated to go unreported each year.

Swimming is the second most popular form of exercise in the United States, with approximately 400 million pool visits annually.³ Although a fecal accident by a swimmer can expose other swimmers to a variety of infectious organisms, cryptosporidia are the most likely to spread infection because they are extremely resistant to chlorine and may remain infective for several days in swimming pool water, even if it contains the recommended amounts of chlorine.⁴ Other parasites known to cause infection via swimming pool fecal contamination include Giardia intestinalis and Escherichia coli.

Fecal contamination is more likely to occur in pools where there are diaper- and toddler-aged children swimming. Diarrheal accidents are much more likely to contain cryptosporidia or other parasites than are formed fecal accidents. The most common route of transmission for these parasitic diseases is swallowing contaminated water. In addition to swimming pools, disinfected water venues where parasitic infections can be spread include waterparks, fountains, hot tubs, and spas.

The CDC makes several recommendations to pool managers and swimmers to reduce the risk of transmitting or contracting parasitic diseases:

· Individuals with diarrhea should not swim.

· Swimmers should avoid swallowing pool water.

· Persons should practice good hygiene before swimming, after using the restroom, and after changing a diaper.

· If a fecal accident occurs, swimmers are advised to leave the pool and not to re-enter until decontamination procedures are completed.

The symptoms of cryptosporidiosis include diarrhea, abdominal cramps, loss of appetite, nausea and vomiting.