Illinois health officials are reminding the public to practice good hygiene before diving into swimming pools.
Chlorine kills most germs. But some, such as a parasite commonly known as Crypto, can survive in pools for days.
The Illinois Department of Public Health says even the best maintained pools can spread illnesses.
You can stay healthy by not swallowing pool water. And swimmers can keep germs out of the pool by showering with soap before swimming, and by washing hands after using the toilet or changing diapers.
If you've been swimming recently and start to have symptoms such as diarrhea, nausea, vomiting, fatigue and fever, check with a doctor and contact your health department.