How are Recreational Water Illnesses (RWIs) Spread?
Swallowing water that has been contaminated with feces containing germs can cause diarrheal illness.
Swimmers share the water—and the germs in it—with every person who enters the pool. On average, people have about 0.14 grams of feces on their bottoms 1 which, when rinsed off, can contaminate recreational water. In addition, when someone is ill with diarrhea, their stool can contain millions of germs. This means that just one person with diarrhea can easily contaminate the water in a large pool or water park. Swallowing even a small amount of recreational water that has been contaminated with feces containing germs can make you sick. Remember, chlorine does not kill germs instantly, and some germs, such as Cryptosporidium (or "Crypto"), are extremely chlorine tolerant.
In addition, lakes, rivers, and the ocean can be contaminated with germs from sewage spills, animal waste, and water runoff following rainfall. Some common germs can also live for long periods of time in salt water.
Many other RWIs (skin, ear, eye, respiratory, neurologic, wound, and other infections) are caused by germs that live naturally in the environment (for example, in water and soil). If disinfectant levels in pools or hot tubs are not maintained at the appropriate levels, these germs can multiply and cause illness when swimmers breathe in mists or aerosols of or have contact with the contaminated water.
For more information on recreational water illnesses, including brochures, posters, and educational materials, please see Healthy Swimming's Resources and Publications page.
1. Gerba, CP. 2001. Assessment of Enteric Pathogen Shedding by Bathers during Recreational Activity and its Impact on Water Quality. Quant Microbiol. 2:55-68.
Get email updates
To receive email updates about this page, enter your email address:
- Centers for Disease Control and Prevention
1600 Clifton Rd
Atlanta, GA 30333
TTY: (888) 232-6348
- Contact CDC–INFO
- For more information, please contact us at healthyswimming@