The fecal parasite cryptosporidium is increasingly being found in public pools, according to the Centers for Disease Control.

Federal health officials are sounding the alarm, asking the public to take extra precautions this summer as they venture into public pools. The CDC said that cases of cryptosporidiosis, which can cause watery diarrhea for up to three weeks, have been increasing 13 percent every year.

The parasite behind the outbreak is called cryptosporidium. It’s spread by bathers who have or have had diarrhea within the previous two weeks. Unfortunately, it can survive in chlorinated public pools.

“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.

It only takes a small amount of infected fecal matter to contaminate an entire pool or hot tub, and in the case of a public swimming facility that uses only one filtration system for multiple pools, 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 reported uptick in cases follows a review of 444 cryptosporidiosis outbreaks within 40 states and Puerto Rico from 2009 to 2017, with cases peaking during the summer months of July through August. This amounted to 7,465 cases, 287 hospitalizations, and one death, the CDC said.

Andy Berg is Executive Editor of Athletic Business.