A: There are many illnesses that children and adults can catch in swimming pools, water parks, hot tubs, lakes, rivers and oceans. These include infections of the skin, eyes, ears, respiratory system, gastrointestinal system and neurological system, which can lead to symptoms such as skin rashes, pinkeye, earache, cough, headache and, most commonly, diarrhea. Usually the illnesses are mild, but they can be life-threatening, especially in pregnant women, young children, the elderly and people with lowered immunity.

Over the past 20 years, the rate of illnesses associated with recreational swimming, especially diarrhea, has increased dramatically. In disinfected swimming areas, such as pools and water parks, chlorine disinfectant certainly helps kill germs. But there may be poor maintenance of the facility and inadequate levels of disinfectant. And even with adequate levels, some germs are resistant to chlorine. In addition, non-disinfected swim areas such as lakes, rivers and oceans can be contaminated by animals defecating nearby or by sewage flow. In all settings, infants and toddlers can spread germs through bowel movements in their diapers, which leak into the water.

The Centers for Disease Control has an initiative to promote healthy swimming (see www.cdc.gov/healthyswimming). Some of the key messages are:

• Don't swim when you have diarrhea. This is especially important for children in diapers. The germs in diarrhea spread easily through the water to other people.
• Don't swallow swimming water or spout water from your mouth. That's a common way that diarrhea is spread.
• Follow good bathroom hygiene. Frequently change baby's diaper and take your children to the bathroom. Change diapers in the bathroom, away from the water. Wash your baby's bottom well after changes and before swimming. Be sure to wash your hands and your child's after changing diapers and using the toilet.
• Consider taking a shower before and after swimming. This can wash germs off your body and help prevent illnesses.