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CDC Warns of Hard-to-Kill Poop Parasite on the Rise in Public Pools

As pool season kicks into high gear, you'll want to be extra careful not to accidentally gulp any of the water this year...

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As pool season kicks into high gear, you'll want to be extra careful not to accidentally swallow any of the water this year. Officials are warning that a tough-to-kill fecal parasite frequently transmitted via swimming pools is on the rise, and that if transmitted, can leave you suffering from "profuse, watery diarrhea" for up to three weeks.

Sorry if you were eating just now.

Outbreaks of the poop parasite known as cryptosporidium have been steadily going up for the last 10 years, according a new report from the Centers for Disease Control & Prevention (CDC), released Friday. It causes cryptosporidiosis, which can lead to the extended bout of diarrhea.

The report states the number of outbreaks has risen an average of 13% each year since 2009 and that most folks tend to catch it at public swimming pools and water parks. What's more troubling, standard chlorination doesn't kill it and it can survive in a properly treated pool for up to a week.

"The number of treated recreational water-associated outbreaks caused by cryptosporidium drives the summer seasonal peak in both waterborne cryptosporidiosis outbreaks and cryptosporidiosis outbreaks overall," reads part of the CDC report. Affected pools can be decontaminated using hyperchlorination methods, it says.

Outbreaks are caused by infected swimmers (folks with diarrhea), who haven't waited an appropriate amount of time after their symptoms subside (at least two weeks) and subsequently excrete the parasite in pools. Others are infected by accidentally ingesting 10 or fewer parasite eggs, which is much easier than you might think.

While symptoms of infection are obviously unpleasant, cryptosporidiosis is almost never fatal. Still, of the 156 water-related outbreaks and 4,232 subsequent cases that have been documented since 2009, it's led to 183 hospitalizations. It's also worth noting that while pools are the leading source of infections, outbreaks have also been linked to livestock, childcare settings, and food (mostly via unpasteurized milk and apple cider). 

So, does this mean you should scrap your swimming plans this summer? Not necessarily. Just please, for the love of canon balls, don't go swimming if you have diarrhea or had it recently.  

To put your risk in perspective, the CDC estimates that there are 309,000 public swimming pools in America. That means that the chances any one of them has had a documented cryptosporidium case in the last 10 years is just 0.05%.

Frankly, that's a slight risk we're willing to take. Especially when it's 95 degrees. 

Just, ya know, don't drink the water.

h/tCNN, Ars Technica


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Joe McGauley is a senior writer for Thrillist. Follow him @jwmcgauley.