Recreational Water Illnesses

Outdoor image of rocky shorelineRecreational water illnesses (RWIs) can be caused by germs and bacteria in the waters that we swim in. People can be exposed through accidental ingestion of water, breathing in aerosols from the water, or just coming into contact with the contaminated water.



What are recreational water illnesses and how do I get them?

Recreational water illnesses (RWIs) can be caused by germs and chemicals present in the water where we swim. People can become ill after accidental ingestion of water, breathing in small water droplets or aerosols, or just coming into contact with contaminated water in swimming pools, hot tubs, water parks, water play areas, interactive fountains, lakes, rivers, or oceans.

Recreational water illnesses can include a wide variety of conditions, including gastrointestinal, skin, ear, respiratory, eye, neurologic, and wound infections. They can also include illnesses caused by exposure to chemicals or toxins, such as byproducts of pool disinfection chemicals in the air, or toxins produced by blue-green algae during harmful algal blooms. While this list is extensive, some waterborne illnesses are much more common than others. The most commonly reported RWI is diarrhea. Diarrheal illnesses can be caused by germs such as Crypto (short for Cryptosporidium), Giardia, Shigella, norovirus and E. coli.

Most RWIs occur seasonally, with the highest number of illnesses reported during the summer months. This is because more people go swimming and enjoy other water-related activities during that time as well. Some RWIs are more commonly associated with chlorinated water venues, but RWIs can occur after exposure to any kind of water body including lakes and rivers.

Who is at risk of getting a RWI?

While anyone who enters contaminated water is potentially at risk for some illnesses, for illnesses where ingestion of the germ is required, people who allow contaminated water to enter their mouth are more likely to become ill, even if they don't swallow it. You can also become ill if contaminated water gets splashed up your nose or you put your head under water. Some germs are so infectious it only takes a tiny bit of contaminated water to make you sick. Children have higher risk of illness because they are more likely to swallow water, splash, and be active in the water.

Why doesn't the chlorine kill all the germs?

Many people think that chlorinated water is sterile and that all germs that enter the water are killed instantly. However, some germs survive for longer periods of time in chlorinated water than others. While most pathogens are inactivated by typical chlorine concentrations in pools within a few minutes, Crypto is extremely chlorine-tolerant and can survive up to 11 days in the water. For this reason, Crypto has become the number one cause of recreational water associated outbreaks in the United States. In untreated water, such as lakes or oceans, germs often survive longer until they are broken down by sunlight or heat.

Where are these germs coming from?

Most of the germs that cause RWIs are brought into the water by infected people, animals, or wastewater runoff. Some germs naturally live in water and can cause illness when their presence is not managed correctly or in people who are more likely to become sick, such as the elderly, small children, and people with immune-compromising conditions.

It is extremely important not to swim while you have diarrhea, because you could be the person who brings germs into the pool that can make other people sick. More than one in five (21.6%) American adults do not know that swimming while ill with diarrhea can heavily contaminate water in which we swim and make other swimmers sick. You don't have to have an accident in the pool to contaminate the pool.

If you have an accident in the pool or see someone have an accident, tell a lifeguard or staff member immediately so that the pool can be cleaned and treated. A single diarrheal accident can introduce over 10 million Crypto organisms into the water—enough to cause infection with a single mouthful of pool water. If we work together, we can help prevent others from becoming sick.

How can we prevent RWIs?

In recreational water, it is important to remember that chlorine and chemicals do not kill the bacteria and germs instantly, and when sweat and urine exist in the pool, the chlorine will lose its effectiveness. To protect everyone near and around the swimming area, swimmers need to take measures to keep those germs out of the water.

For general public:
  • Keep the poop, germs, and pee out of the water.

  • Don't swim when you have diarrhea (and don't swim for two weeks after illness if you have Crypto).

  • Don't pee in the pool.

  • Shower with soap before you start swimming and wash your rear end well! Be sure to rinse before you get back in the water.

  • Wash your hands after using the toilet.

  • Don't swallow the water you swim in.

For parents of young children:
  • Remember that swim diapers DO NOT prevent germs from rinsing into the water.

  • Take the children on bathroom breaks every 60 minutes or check diapers every 30-60 minutes.

  • Change diapers in the bathroom or diaper changing areas and NOT at poolside to reduce the risk that germs can rinse into the water.

  • Wash your child well with soap and water (especially the rear end) before returning to the pool.

  • Wash your hands after using the toilet or changing diapers.

  • Educate your children not to swallow the water they swim in.


For more information:

Common Causes of Recreational Water Illnesses

CDC's Healthy Swimming Page

Recreational Water Safety Homepage

Environmental Health Homepage

Last Revised: July 3, 2018