The U.S. saw 90 outbreaks of illnesses associated with pools and hot tubs between 2011 and 2012, a number that has has “significantly increased,” officials said.

The Centers of Disease Control and Prevention released a report this week on the outbreaks, which spanned 32 states and Puerto Rico, led to 1,788 cases, 95 hospitalizations, and one death. Half of the incidents associated with treated recreational water—pools and hot tubs—were caused by cryptosporidium, a parasite found in fecal matter that causes diarrhea. That’s a large increase since the first cryptosporidium-related outbreak was detected in 1988, the CDC said.

According to CBS News, the CDC issued a 2014 report that recommends the installation of ultraviolet light, ozone, or some other supplemental disinfectant to kill germs like cryptosporidium.

The best way to keep swimmers and swimming facilities healthy, according to the CDC:

Stay out of the water if you have diarrhea.

Shower before you get in the water.

Don’t pee or poop in the water.

Don’t swallow the water.

Get our Health Newsletter. Sign up to receive the latest health and science news, plus answers to wellness questions and expert tips. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.