CDC Warning: Parasite Found In Public Swimming Pools On The Rise


One of the greatest pleasures of summer is cooling off in the pool or spending the day at a water park with your family, but government health officials warn that there are parasites lurking in communal water that not even chlorine can kill.

There is a fecal parasite that sickens people through contaminated swimming pool water is on the rise across the U.S., prompting federal health officials to warn the public to take extra precautions this summer.

Even in a well chlorinated pool, the Giardia parasite can survive for up to 45 minutes, and the hepatitis A virus can survive for about 16 minutes, according to the Centers for Disease Control and Prevention. A parasite called cryptosporidium, or crypto, can survive for more than a week even in a properly treated pool or water park, according to epidemiologist Michele Hlavsa.

Exposure to crypto in pools and water playgrounds caused 4,232 illnesses from 2009 to 2017, according to a report released Thursday by the CDC. People, children in particular, who swim too soon after having a case of diarrhea can spread the parasite.

The parasite behind the outbreak, cryptosporidium, is spread by bathers who have or have had diarrhea within the last two weeks. But unlike other germs, this parasite can survive in well-maintained chlorinated pools for up to a week.

This 1983 microscope image provided by the Centers for Disease Control and Prevention shows Cryptosporidium parvum parasitic organisms in a stool smear specimen, the cause of a patient’s cryptosporidiosis. Associated Press

“People have an average of 0.14 grams of poop on their bottoms. This poop can wash off swimmers’ bodies and can contaminate the water with germs,” the CDC warns.

“Unlike maybe norovirus or E. coli, which cause diarrhea or vomiting for a couple days, you can have diarrhea caused by crypto for up to three weeks,” said Hlavsa, one of the study’s authors. “That’s not fun.”

The number of illnesses caused by crypto associated with “treated recreational water” peaks from June to August and increased 14.3% each year from 2009 to 2016, according to the CDC. The report noted that these findings probably underestimate the actual number of crypto outbreaks.

It only takes microscopic amounts of this infected fecal matter to contaminate an entire pool or hot tub. If a public swimming facility uses one filtration system for more than one pool, it could spread to all of them.

“This means that a single diarrheal incident from one person could contaminate water throughout a large pool system or waterpark,” the CDC states. “That is why it is so important to stay out of the pool if you are sick with diarrhea, shower before swimming, and avoid swallowing pool water.”

The CDC advises anyone who’s had diarrhea to wait at least two weeks before getting into a pool, but a recent survey found that 24% of respondents would go in a pool within one hour of having diarrhea.

Cover photo: Vitaly Raduntsev/Shutterstock (edited)