Fifty-eight percent of pool filter samples tested positive for E. coli
A study of public pools done during last summer’s swim season found that feces are frequently introduced into pool water by swimmers. Through the study, released by the Centers for Disease Control and Prevention (CDC), researchers found germs in samples of pool filter water collected from public pools.
CDC collected samples of water from pool filters from public pools and tested the samples for genetic material (for example, DNA) of multiple microbes. The study found that 58% of the pool filter samples tested were positive for E. coli, bacteria normally found in the human gut and feces. E. coli is a marker for fecal contamination.
Finding a high percentage of E. coli-positive filters indicates swimmers frequently contaminate pool water when they have a fecal incident in the water or when feces rinse off of 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 strain that causes illness.
Pseudomonas aeruginosa, which can cause skin rashes and ear infections, was detected in 59% of samples. Finding P. aeruginosa in the water indicates natural environmental contamination or contamination introduced by swimmers. Cryptosporidium and Giardia, pathogens that are spread through feces and cause diarrhea, were found in less than 2% of samples. The tests used in the study do not indicate whether the detected germs were alive or able to cause infections. Indoor and outdoor public pools were sampled.
The study did not address water parks, residential pools or other types of recreational water. The study does not allow CDC to make conclusions about all pools in the U.S. However, it is unlikely that swimmer-introduced contamination or swimmer hygiene practices differ between pools in the study and those in the rest of the country.
“Swimming is an excellent way to get the physical activity needed to stay healthy,” said Michele Hlavsa, chief of CDC’s Healthy Swimming Program. “However, pool users should be aware of how to prevent infections while swimming. Remember, chlorine and other disinfectants don’t kill germs instantly. 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.”
This study is presented in recognition of Recreational Water Illness and Injury Prevention Week, May 20 to 26, 2013. The goal of the prevention week is to raise awareness about healthy swimming, including ways to prevent recreational water illnesses (RWIs). Germs that cause RWIs are spread by swallowing, breathing in the mists or aerosols from, or having contact with contaminated water in swimming pools, water parks, hot tubs, interactive fountains, water play areas, lakes, rivers or oceans.
Click here  to view the report and CDC recommendations to swimmers.