Are Parasites Swimming in Your Public Pools and Water Parks?

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Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: Dennis Lee, MD

A state-run water park in upstate New York was temporarily closed after hundreds of visitors to the park, mostly children and teens, developed a gastrointestinal illness. The tank system at the water park was shown to be contaminated with Cryptosporidium, a parasite that was later isolated from several of the victims and believed to responsible for the outbreak of the illness.

Cryptosporidiosis (both the infection and the organism are sometimes referred to as "crypto") is the disease caused by parasites of the genus Cryptosporidium. Some of the most frequent symptoms of waterborne diseases in the U.S., cryptosporidiosis cause:

• watery diarrhea
• nausea,
• vomiting,
• fever, and
• stomach cramps.

As a result of the diarrhea and vomiting, people with cryptosporidiosis often become dehydrated and may lose weight.

The organism lives in the intestine of infected persons or animals and is passed in the stool (feces). Cryptosporidia are very hardy organisms that can live outside the body for long periods and can survive in the presence of chlorine and many common disinfectants. The organism has been found in drinking water and swimming pools throughout the world and all over the U.S. It is spread by contact with water, food, soil, or surfaces that have been contaminated with infected stool (feces). A person gets the infection by swallowing the parasite, either from putting something contaminated into the mouth or from swallowing contaminated water. In addition to pools and hot tubs, it is possible to get the infection from any type of "recreational" water including lakes, rivers, and the ocean.

Symptoms of cryptosporidiosis usually last one to two weeks and begin two to 10 days after infection. Some people who become infected never experience any symptoms, but they can still transmit the disease to others. Cryptosporidiosis can be highly contagious; infected persons should practice good hygiene and avoid swimming in pools, lakes, hot tubs, or in the ocean for at least two weeks after the symptoms have ended.

The diagnosis of cryptosporidiosis is made by examination of stool specimens. Most people who have a healthy immune system recover from cryptosporidiosis on their own without specific treatment. Those with compromised immune systems, such as people with HIV or who are receiving chemotherapy for cancer or other immunosuppressive drugs, have a risk of developing a more serious, potentially life-threatening, illness from the infection.

You can help to keep public pools and other summer water and swimming activities safe and healthy by doing the following:

• Don't swim if you have diarrhea. This is especially important for children or babies in diapers.
• Don't swallow pool water. Try to avoid getting any water in your mouth.
• Practice good hygiene. Shower before swimming and wash your hands after using the toilet or changing diapers.
• Take your children on bathroom breaks often. Check diapers often and change them when necessary.
• Change diapers in a bathroom, not by the pool. Germs can spread to objects and surfaces in and around the pool.
• Wash your child thoroughly (especially their bottom) with soap and water before taking them into the pool. Everyone has invisible amounts of fecal matter on their bottoms, and it ends up in the pool!

Originally published in August 2005.

REFERENCES: Centers for Disease Control