ATLANTA, June 29 (UPI) -- The Centers for Disease Control is warning swimmers to shower before going into the pool in order to avoid spreading the chlorine-resistant pathogen cryptosporidium, which has caused several outbreaks in recent years.
While E. coli and norovirus are killed within hours by chemicals used for treating pools, cryptosporidium survives in pools and hot tubs for up to ten days, and can cause gastrointestinal problems such as diarrhea.
"This parasite is extremely chlorine-resistant," Michele Hlavsa, an epidemiologist at the CDC, told CBS News. "Swimmers bring it into the water when they are sick with diarrhea."
Researchers reviewed data from 2011 and 2012, finding that 90 outbreaks related to recreational water resulted in at least 1,788 cases, 95 hospitalizations and 1 death, according to the CDC's study, which is published on its website.
Of the outbreaks, 77 percent of them were in treated bodies of water such as pools and spas.
Cryptosporidium was responsible for 52 percent of the treated water outbreaks, and was also responsible for 54 percent of all the outbreaks cause by infectious pathogens.
"Since 1988, the year that the first U.S. treated recreational water-associated outbreak of Cryptosporidium was detected, the number of these outbreaks reported annually has significantly increased," researchers wrote in the report.
If contracted, the parasite can be cleared from the body in about two to three weeks, however it can be fatal in a person with a weakened immune system, Hlavasa said.
"With these outbreaks, we see they disproportionately affect young children," Hlavasa told ABC News. "They're the ones who can go to a pool and young children tend to carry lots of germs."
The CDC recommends swimmers shower before entering the pool, not swallow the water, and not urinate or defecate in the water while swimming; swimmers are discouraged from entering pools altogether if they have diarrhea.