Are Parasites Swimming in Your Public Pools and Water Parks?

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Every year many cases of Cryptosporidium are reported to state health departments. Over the years several water parks had to temporarily close their pool facilities due to contamination and large outbreaks of Cryptosporidium infections.

Cryptosporidiosis (both the infection and the organism are sometimes referred to as "crypto") is the disease caused by parasites of the genus Cryptosporidium. Infection with these organisms produces gastrointestinal symptoms including:

As a result of the diarrhea and vomiting, people with Cryptosporidiosis often become dehydrated and may lose weight. An estimated 748,000 cases of Cryptosporidiosis occur every year in the US.

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 of time 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.

Cryptosporidiosis is spread by contact with water, food, soil, or surfaces that have been contaminated with infected stool (feces). A person (or animal) contracts 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. Hikers who drink from untreated natural water sources are at risk for infection.

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. Others will have on and off symptoms for a month or more. 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 resolved.

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.
  • Shower before entering a 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. REFERENCE: Centers for Disease Control.

Previous contributing editor: Dennis Lee, MD.


Last Editorial Review: 5/30/2012



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