CDC: Watch Out for Pool Parasites

May 19, 2008 -- Just before the Memorial Day weekend kicks off summer's unofficial start, the CDC is urging people to brush up on their pool hygiene.

Last year, the CDC got a record number of reported outbreaks of recreational water illnesses, which are spread by swallowing, breathing, or having contact with germs in the water of swimming pools, spas, lakes, rivers, or oceans.

So far, the CDC has reports of 21 outbreaks of cryptosporidium ("crypto"), the leading cause of recreational water illnesses. That number includes 18 crypto outbreaks linked to chlorinated pools, water parks, or other treated recreational water facilities. The other three outbreaks were linked to lakes.

Those are preliminary figures; the actual number of outbreaks is likely greater, CDC epidemiologist Michele Hlavsa, RN, MPH, tells WebMD. The CDC also got reports of more than 25 recreational water illness outbreaks not caused by crypto in 2007.

An outbreak involves at least two cases linked to the same exposure, notes Hlavsa, adding that in 2007, a crypto outbreak in Utah involved more than 1,900 lab-confirmed cases.

The CDC's preliminary data show that during 2004-2007, the number of reported crypto cases tripled and the number of crypto cases linked to swimming pools more than doubled.

Crypto Risk

Crypto can cause watery diarrhea lasting for one to three weeks, stomach cramps or pain, dehydration, nausea, vomiting, fever, and weight loss. Symptoms generally start within two to 10 days after infection.

Crypto spreads by swallowing tainted water or by putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or an infected animal. It's not spread through contact with blood.

"The most important thing we can do is to keep crypto out of the water," Hlavsa says. "Even in a well-maintained pool, crypto can survive for 10 days" because it resists chlorine.

"Despite the fact that there's chlorine in the water, the water's not sterile. It's not drinking water," Hlavsa says.

Pool Hygiene

The CDC provides these tips for preventing recreational water illnesses:

• Don't swim when you have diarrhea. Don't get back in the water until two weeks after the diarrhea has ended.
• Don't swallow pool water. Avoid even getting the water in your mouth.
• Take a shower before swimming.
• Wash your hands after using the toilet or changing diapers.
• Take your kids on bathroom breaks or check diapers often.
• Change diapers in a bathroom or diaper-changing area, not by the pool.
• Wash your child thoroughly (especially their rear end) with soap and water before swimming, even if they look clean.