CDC Issues Warning forbr ‘Crypto’ Fecal Parasite in Pools Health officials in the USA are warningbr people of a parasite, cryptosporidium,br that can potentially cause chronic diarrhea. Infected healthy adults will experience "profuse,br watery diarrhea" for as long as three weeks, with the effects being worse forbr children, pregnant women and thosebr with compromised immune systems. Cryptosporidium has a high tolerancebr to chlorine and can survive in abr chlorinated pool for up to seven days. The parasite enters the body throughbr ingestion of contaminated water. Between 2009 and 2017, 7,465 peoplebr fell ill due to outbreaks, with recreationalbr water responsible for a third of the outbreak cases. CDC, via statement Although it is considered to be almostbr never fatal, one death was reported in 2009br and 287 people have been hospitalized.