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