Now that swimming season is upon us, all sorts of nasty surprises can come with the opening of the pools. According to the Center for Disease Control (CDC), there is a parasite lurking in the chlorine-filled water. Crypto, the name given to this parasite, is able to survive up to ten days in pool water, the CDC reports.

Jaima Ballentine, a manager at HML Labs, warned that there are several unpleasant symptoms associated with this parasite.

“You’re going to have stomach cramping, diarrhea, vomiting.”

Crypto is said to be spread through human feces and has had a tremendous growth in outbreaks recently. There have been 32 outbreaks in the last year linked to swimming pools and water playgrounds.

Ballentine recommends that individuals plan to treat their pools regularly, which falls in like with the common theme that pool-owners should clean once a week during swimming seasons.

However, with regular cleaning not being enough to remove this particular parasite, the CDC recommends taking extra measures.

Michele Hlavsa, chief of the CDC’s Healthy Swimming Program, had this to say.

If you do notice your family and friends getting sick after they take a dip in your pool, the CDC endorses rectifying the damage with hyperchlorination. And while this might go without saying, if you’re sick, don’t swim.

Hyperchlorination in this instance is the act of mixing a higher dosage of chlorine into the water than normal, to purge it of all bacteria and parasitic presence.

Unfortunately, there is no way to detect a small amount of Crypto in the pool. This is because the parasite does not evenly spread throughout the water you’re testing. The only way to know for sure if your pool is infected is to wait and see if symptoms begin to appear.

And it can take nearly a week at times for these symptoms to appear.

The best way to combat the infection is to remove the source, according to the CDC. Don’t allow anyone in the pool without first making them bathe, to prevent human fecal matter from being exposed to the water.