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Recreational Water Illness & Prevention

Recreational Water Illnesses (RWIs) are caused by germs that can contaminate water in swimming pools, whirlpool spas, hot tubs, water parks, water play areas, interactive fountains, lakes, rivers, or beaches. These germs can be spread by swallowing, breathing in mists or aerosols, or having contact with contaminated water. The most commonly reported RWI is diarrhea caused by germs such as Cryptosporidium, Giardia, Shigella, Norovirus, and Escherichia coli 0157:H7.

The chlorine used in swimming pools kills most of the germs that cause RWIs, but chlorine doesn't work right away. It takes time for chlorine to kill germs, and pool operators need to regularly measure chlorine and pH levels to make sure they are effective for killing germs in pool water. Even if a pool is properly chlorinated, the germ Cryptosporidium can live in pool water for days and cause illness. The chemicals used to treat recreational water can also cause illness if they are not properly handled.

The Health Department encourages swimmers, pool owners and aquatics staff to take steps for a healthy swimming experience.

Swimmers: Follow the Triple A's of Healthy Swimming

Do not swim in areas where there are no lifeguards or when a beach is under an advisory or closure. To find out if a NYC beach is "Open for Swimming and Wading," "Under Advisory," or "Closed" call 311, sign-up for text notifications, text Beach to 877-877 or check out our NYC Area Beach Map.

► Awareness+

  1. Do not swim when you have diarrhea. This is especially important for kids in diapers. Don't swim until two weeks after you stop having diarrhea.
  2. Do not swallow pool water or get pool water in your mouth.
  3. Shower with soap before swimming. Wash children thoroughly (especially the rear end) with soap and water before swimming.
  4. Wash your hands after using the toilet or changing diapers.
  5. Take children on bathroom breaks or change diapers often.
  6. Change children's diapers in a bathroom, not at poolside.

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► Action+

  1. Ask the pool operators if free chlorine and pH levels are checked at least 3 times per day and more often when the pool is heavily used, and request information on the latest pool inspection results.
  2. You can also check pool water yourself using test strips purchased at your local hardware or pool supply store. For more information on test trips Visit: Triple A's of Healthy Swimming.

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► Advocacy+

  1. Educate other swimmers about RWIs to promote healthy swimming.
  2. Encourage pool operators to take steps known to kill germs that cause RWIs.

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Awareness of recreational water illnesses and healthy swimming behaviors play an important role in stopping the spread of RWIs. Germs on swimmers' bodies end up in the water and can make other people sick. Cryptosporidium and other germs that cause diarrheal illness can be spread when swimmers swallow water contaminated by a person with diarrhea. Even healthy swimmers can get sick from RWIs, but the young, elderly, pregnant women and immunosuppressed persons are especially at risk.

Recreational water sites are important places for exercise and leisure. The Health Department and the Centers for Disease Control and Prevention urge swimmers to continue to enjoy swimming, but only after adopting healthy swimming behaviors to reduce the risk of getting sick due to a recreational water illness, and to prevent other swimmers from getting sick.

Other Swimming Info

Pool Owners and Aquatics Staff

Recommendations for public swimming pool staff include improved operations, specialized training for all pool operators and public education to protect swimmers from infectious disease transmission.

►Implement operational and prevention measures+

Water quality should be regularly monitored and controlled. If water quality does not meet the legal requirements or exceeds the regulated limits, the pool should be closed until the condition is corrected. Even a well maintained pool can transmit Cryptosporidium. Typical levels of chlorine in a pool and normal pool filtration are not effective against Cryptosporidium, so efforts to increase swimmer awareness and participation in healthy swimming habits are essential.

  • Free chlorine and pH levels should be checked at least three times a day and more often when the pool is in heavy use.
  • Make Healthy Swimming posters and brochures accessible to all swimmers.
  • Have a written response policy to address feces, vomit and blood contamination incidents.

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►Take measures to prevent pool chemical-related injuries+

Chemicals added to pool water help provide protection against germs and improve water quality. However, these same chemicals can also cause injuries if they are not properly handled. Pool chemical-related injuries lead to thousands of emergency room visits each year. Public pool operators and residential pool owners can protect themselves and swimmers by taking these key steps:

  • ALWAYS secure pool chemicals: Keep children and animals away.
  • ALWAYS read product name and manufacturer's directions before each use.
  • ALWAYS use appropriate protective gear, such as safety glasses and gloves, when handling pool chemicals.
  • NEVER mix chlorine products with each other, acid, or other substances.

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To access a complete set of recommendations to prevent pool chemical-related injuries, visit the CDC website:

More Beach and Pool Information