Summer is here, meaning pool season is here, meaning ... hello, parasite overlords? Per USA Today, the CDC reports that each year, between June and August, there's a marked increase in the number of sicknesses from the cryptosporidium, or crypto, parasite found in "treated recreational waters." And from 2009 to 2016, that number steadily rose, increasing 14.3% each year. Crypto isn't the only creeper, either: The giardia parasite also lurks in pools, and both parasites are chlorine resistant, with giardia able to survive up to 45 minutes in a well-chlorinated pool, while crypto can stick it out in the water for more than a week. If you get infected? "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," report author Michele Hlavsa says. "That's not fun."
How the resulting "recreational water illnesses," or RWIs, come about, per the CDC: Swimmers swallow water that has fecal matter in it, typically from a person who's had a recent episode of diarrhea. Although the CDC says anyone who's had diarrhea can potentially spread their germs for up to two weeks, a recent survey showed that nearly a quarter of respondents would dive back into the water just an hour after having an episode. "We want to keep crypto out of the pool in the first place, and the way we do that is not to swim or let our kid swim when we're sick with diarrhea," Hlavsa tells USA Today. A furrier demographic has also been susceptible lately to the giardia parasite, though not from swimming pools: Per CBS Chicago, veterinarians in the Windy City last month noticed an uptick in infection in pets, likely due to standing water in the streets left by lots of recent rain. (Read more swimming pool stories.)