Researchers at the Centers for Disease Control and Prevention in Atlanta collected samples of water from pool filters from public pools and tested the samples for genetic material -- DNA of multiple microbes -- and found 58 percent of the pool filter samples tested were positive for E. coli, a marker for fecal contamination.
Michele Hlavsa, chief of CDC's Healthy Swimming Program, said finding a high percentage of E. coli-positive filters indicated swimmers frequently contaminate pool water when they have a fecal incident in the water or when feces rinses off their bodies because they do not shower thoroughly before getting into the water. No samples tested positive for E. coli O157:H7, a toxin-producing E. coli strain that causes illness, the study said.
In addition, the testing found pseudomonas aeruginosa, which can cause skin rashes and ear infections, was detected in 59 percent of samples. Cryptosporidium and Giardia, germs that are spread through feces and cause diarrhea, were found in less than 2 percent of samples.
The tests used in the study did not indicate whether the detected germs were alive or able to cause infections.
The study did not address water parks, residential pools or other types of recreational water, Hlavsa said.
"Remember, chlorine and other disinfectants don't kill germs instantly," Hlavsa said in a statement. "That's why it's important for swimmers to protect themselves by not swallowing the water they swim in and to protect others by keeping feces and germs out of the pool by taking a pre-swim shower and not swimming when ill with diarrhea."
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