"People who swim too soon after recovering from diarrhea — or even while they are still sick — are spreading a waste-born parasite in public pools and water parks, federal health experts said Thursday.

Outbreaks of cryptosporidium doubled between 2014 and 2016, and three outbreaks from last summer demonstrate the problem, the Centers for Disease Control and Prevention said.

'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.

'Crypto is the most common cause of diarrheal illness and outbreaks linked to swimming pools or water playgrounds because it is not easily killed by chlorine and can survive up to 10 days in properly treated water,' the CDC added."

Maggie Fox reports for NBC News May 18, 2017. [2]