CDC researchers analyzed samples taken from pool filters in public pools in Atlanta, Georgia, and 58 percent of them were contaminated with E. coli, a bacteria found in human feces. It's not just feces. Other swimmers are also urinating in the pool. "Chlorine and other disinfectants don't kill germs instantly," said Michele Hlavsa, chief of the CDC's Healthy Swimming Program. "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.