Attention swimmers: A high percentage of public pools tested in a new study contained bacterial evidence that someone may have pooped in the pool.

The Centers for Disease Control and Prevention collected samples from pool filters at 161 pools in the metro-Atlanta area last summer. Some of the pools were public, some were in private clubs and some were in water parks.

Among the samples, 93 -- or 58% -- contained E. coli, a bacterium that lives in the digestive tract of humans and other warm-blooded animals. The researchers treated the presence of E. coli as "a fecal indicator," they wrote in their report.

It's likely that swimmers delivered some of it into the water by failing to take a thorough, soapy shower before getting into the pool.

The testing did not indicate whether the germs were alive and capable of causing infection and disease. But the presence of fecal matter in pools poses a major health risk because chlorine and other pool cleaning chemicals don't kill bacteria immediately. The bacteria found in human feces that can cause rashes and infections.

To reduce your risk of getting sick, the CDC suggests:

  • Do not swallow the water you swim in.
  • Keep feces and other contaminants out of the water by showering with soap before swimming, washing your hands properly after using the restroom or changing a baby's diapers, and never swimming when you have diarrhea.
  • Keeping chlorine levels at 1 to 3 mg/L or parts per million and the pH at 7.2 to 7.8 to maximize its germ-killing power.
  • Children should be taken to use the bathroom every 60 minutes and diapers should be checked every 30 minutes while at the pool.

For more information, visit the CDC's Healthy Swimming information page.