Of the pools tested, 58 percent of them contained E. coli, a bacteria typically confined in the human gut and feces, Fox reported.
Some fecal bacteria stays on the human body, and gets into the pool from swimmers that do not shower beforehand. There were no instances of the strain of E. coli that produces illness.
"Chlorine and other disinfectants don't kill germs instantly," said Michele Hlavsa, chief of the CDC Healthy Swimming program.
The CDC recommends taking care not to swallow pool water and avoid swimming when they have diarrhea. The report also suggested parents take their young children on a bathroom break every hour, and check babies' diapers every half-hour.
But most importantly, don't poop in the pool.
“It is time to stop treating the swimming pool as a toilet,” Hlavasa told NBC News. “Nowhere else except for the pool is it acceptable to poop in public or pee in public. In other places if we did this in public, we’d be arrested.”