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Recreational Water Illnesses (RWIs)

Recreational Water Illness (noun):

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Dad and kids swimming

Contrary to popular belief, chlorine does not kill all germs instantly. There are germs today that are very tolerant to chlorine and were not known to cause human disease until recently. Once these germs get in the pool, it can take anywhere from minutes to days for chlorine to kill them. Swallowing just a little water that contains these germs can make you sick.


RWIs include a wide variety of infections, such as gastrointestinal, skin, ear, respiratory, eye, neurologic, and wound infections. The most commonly reported RWI is diarrhea. Diarrheal illnesses are caused by germs such as Crypto (short for Cryptosporidium), Giardia, Shigella, norovirus and E. coli O157:H7. With RWI outbreaks on the rise, swimmers need to take an active role in helping to protect themselves and prevent the spread of germs. It is important for swimmers to learn the basic facts about RWIs so they can keep themselves and their family healthy every time they swim.

In the past two decades, there has been a substantial increase in the number of RWI outbreaks associated with swimming. Crypto, which can stay alive for days even in well-maintained pools, has become the leading cause of swimming pool-related outbreaks of diarrheal illness. From 2004 to 2008, reported Crypto cases increased over 200% (from 3,411 cases in 2004 to 10,500 cases in 2008) 1.

Although Crypto is tolerant to chlorine, most germs are not. Keeping chlorine at recommended levels is essential to maintain a healthy pool. However, a 2010 study found that 1 in 8 public pool inspections resulted in pools being closed immediately due to serious code violations such as improper chlorine levels 2.

  1. CDC. Cryptosporidiosis surveillance — United States, 2009–2010. MMWR Morb Mortal Wkly Rep. 2012;61(SS05):1-12.
  2. CDC. Violations identified from routine swimming pool inspections — Selected states and counties, United States, 2008. MMWR Morb Mortal Wkly Rep. 2010;59(SS19):582-587.
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