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Avoiding Germs in Swimming Pools

Two parasites - Cryptosporidium and Giardia – cause most outbreaks of diarrhea among swimmers in the United States. Cryptosporidium causes particular concern because it's extremely infectious and isn't killed very well by chlorine, which kills many other germs.

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Emerging Infectious Diseases journal, June 2008

A study published in the June 2008 issue of CDC’s journal Emerging Infectious Diseases looked at 160 public pools in the Atlanta area to determine how common the two parasites are, even at times when they aren’t causing outbreaks of illness. Researchers analyzed samples from swimming pool filter systems collected at the end of the swim season and found that one in 12 contained evidence of one or both parasites. With the methods used, the researchers could not determine if these parasites were alive or could cause disease. While 1 in 12 may not seem like a lot, it means that swimmers are coming into contact with these parasites even when health officials don’t realize the germs may be causing illness. Children’s pools, community pools and smaller-sized pools with less water accounted for most of those that were contaminated. Pools that had fewer swimmers per week were also more likely to contain the two parasites.

These parasites are spread when someone swallows pool water contaminated with feces, eats contaminated food or handles contaminated diapers without washing their hands.

Swimmers can follow these basic steps to help protect themselves and other swimmers from these germs:

  • Do not swim when you or your children have diarrhea.
  • Do not swim when you or your children have diarrhea.
  • Don't swallow the pool water and avoid getting it in your mouth.
  • Do not swim when you or your children have diarrhea.
  • Practice good hygiene – take a shower before swimming, take your kids on frequent bathroom breaks, and change babies’ diapers in the bathrooms, not at poolside.

Children and pregnant women can become more severely ill if infected with Cryptosporidium or Giardia. Cryptosporidium infection can be life-threatening in people with compromised immune systems (such as those with AIDS, organ transplant patients, or those receiving certain types of cancer treatments). Other Recreational Water Illnesses cause a wide variety of problems such as skin, ear, eye, and respiratory infections.

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