"The parasite can spread when people swallow something that has come into contact with the feces (poop) of a sick person, such as pool water contaminated with diarrhea", the CDC said in a statement.
The Centers for Disease Control (CDC) found that at least 32 outbreaks of crypto were reported in 2016, compared to 16 in 2014.
"To help protect your family and friends from crypto and other diarrhea-causing germs, do not swim or let your kids swim if sick with diarrhea", said Michele Hlavsa, R.N., M.P.H., chief of CDC's Healthy Swimming Program.
"Normal chlorine disinfection of swimming pool water does a great job in destroying most germs, but Crypto presents a special challenge", said Dr. Chris Wiant, chair of the Water Quality and Health Council.
Even proper chlorination of pools doesn't kill the persistent parasite, the CDC said. She also urged people to protect themselves by avoiding swallowing pool water.
Once a pool or water playground is infected with crypto, it's easy to spread, but not easy to get rid of.
To kill the parasite, the CDC recommends closing pools and treating the water with high levels of chlorine, called hyperchlorination.
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Don't swim if you're sick. Those outbreaks highlight the ongoing challenges that treated recreational water venues have with Crypto due to how hard it is to kill and the small number of germs that can make people sick.
Don't swallow the water while swimming.
Dr. Chris Wiant, chair of the Water Quality and Health Council, advocates for people to shower before getting into a community pool and to not pee while in the pool.
Take kids on bathroom breaks often, and check diapers in a diaper-changing area and not right next to the pool. Arizona identified 352 people sick with Crypto for July-October 2016, compared with no more than 62 cases for any one year in 2011-2015.
CryptoNet, launched in 2010, is the first U.S. DNA fingerprinting-based tracking system for illness caused by a parasite.
Before you cancel your child's swim lessons, however, the CDC said it's not sure what accounts for the rise in recorded outbreaks.
Meanwhile, the only way to ensure your own health is to take precautions when swimming in pools or playing at water parks.