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Pool parasites

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A pool may be cool and a good place to relax on a hot summer day, but even one that looks clean could be swimming in microscopic parasites. Consumer Reports dives into a common cause of a swimming-related illness and tells you what you can do to avoid it.

The most common culprit when it comes to this swimming-related illness — particularly in public pools or water parks — is cryptosporidium or crypto for short. It’s spread through fecal matter; even a small amount can contain millions of germs. Regular levels of chlorine won’t kill crypto, which can survive in a well- maintained pool for up to 10 days. It’s also easy to catch. The Centers for Disease Control and Prevention says that swallowing even one mouthful of water infected with crypto can lead to weeks of diarrhea, nausea, and vomiting. You should emphasize to kids that they should not be swallowing the water.

To protect yourself and your family, make sure anyone who swims in your pool follows some simple guidelines. Anyone who is experiencing diarrhea or has been sick in other ways should not swim. You should have people take a shower or at least rinse off before they swim. Also, have kids take frequent bathroom breaks to reduce the risk of accidents. That goes for babies as well; those swim diapers aren’t foolproof.

If fecal matter does get into the pool, don’t take any chances. Everybody out of the water. Shut it down. The only way to effectively kill crypto is to have a professional super-chlorinate the water and then slowly bring it back to normal levels again, a process that can take at least 8 hours.

If you get sick after swimming, your doctor can run tests to see whether crypto is the cause. If it is, the CDC says you should wait a full two weeks after the diarrhea has stopped before you get back in a pool.

All Consumer Reports material Copyright 2018 Consumer Reports, Inc. ALL RIGHTS RESERVED. Consumer Reports is a not-for-profit organization which accepts no advertising. It has no commercial relationship with any advertiser or sponsor on this site. For more information visit

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