There were twice as many outbreaks reported to CDC in 2016 compared with 2014, researchers from the CDC and from health department in Alabama, Arizona, and OH reported today in the latest issue of Morbidity and Mortality Weekly Report (MMWR).
Infections occur when swimmers ingest water contaminated by diarrhea from a person infected by Cryptosporidium or Crypto, a parasite that is notoriously hard to kill.
"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 caused at least 32 outbreaks in swimming pools or water parks in 2016, compared with 16 in 2014, according to a report published in the U.S. Centers for Disease Control and Prevention's weekly report on death and disease.
For example, parents might spread the parasite if they change a child's crypto-contaminated diaper and then hop in the water without properly washing their hands, Kan said.
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Crypto is the most common cause of diarrhea, the CDC says. The infection can become life-threatening in people with compromised immune systems. One recent study found every pool tested contained urine. 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.
This as a new survey finds 25-percent of adults would swim within one hour of having diarrhea. It's unclear whether the number of outbreaks has increased or whether better surveillance and laboratory methods are leading to better outbreak detection.
OH was one of the most heavily-infected states, according to the CDC, with 1,940 people falling ill due to the infection in 2016 compared to less than 600 in any previous year. "If we're good about doing it at the lake where there is no chlorine in the water, we need to be just as good about reminding our little ones not to swallow the water in the pool", Hlavsa said. The illness can last up to three weeks.
Symptoms of crypto infection include watery diarrhea, stomach cramps, nausea, or vomiting, which can lead to dehydration.
These results are concerning to experts from the CDC, the Water Quality and Health Council, and the National Swimming Pool Foundation due to the concerns over Crypto.
"So, really, this is just a reminder to everyone (that) we have to be smarter about how we swim, and swim healthy, not swim with diarrhea and not swallow the water we swim in", Hlavsa said.