A fun trip to the swimming pool, waterpark, lake, river, or ocean is part of the joy of summer. However, the water that we swim and play in comes in contact with every surface of our bodies and can sometimes carry germs that cause problems long after we dry off. Recreational Water Illnesses (RWIs) are health problems that stem from exposure to certain germs that can be in the water.
Swimmers, waders, and even those near the contaminated waters can be exposed to RWIs by:
- Breathing in water from tiny droplets in the air
- Swallowing water
- Contact with water, especially if skin is vulnerable or injured
Rivers and lakes are more likely than other sources to be contaminated by animal waste, sewage spills, and water runoff following rainfall, but even conventionally safer sources such as hot tubs and splash pads can cause trouble if germ-killing chemicals in the water are not well-maintained. For example, germs that live in the natural environment without causing harm can grow and multiply in a poorly treated hot tub, where their large numbers create much greater risk of illness. There are even some germs that are resistant to the antimicrobial effects of chloride. Pools, spas, and water playgrounds are frequently not as clean as we may believe; in fact, in one study showed that 10% of inspected water facilities were so undertreated they were required to close. The same microbes that are carried in natural waterways can also be transmitted by eating contaminated food and beverages.
Because there are many kinds of germs that cause RWIs, symptoms also vary and depend on the source of the infection. Symptoms will generally start within 10 days of contact with the contaminated water.
Diarrhea and vomiting are common among RWIs. Parasites called Cryptosporidium and Giardia are the most common causes of diarrhea-associated RWIs (accounting for over 50%); however, norovirus and other RWI-associated germs may also cause these symptoms. These germs are most commonly spread by feces in the water. Even very tiny amounts of feces can be dangerous if given the opportunity to multiply and infect in recreational water sources. Studies show that although we clean ourselves thoroughly after using the bathroom, humans carry about 0.14 grams of feces (similar to a few grains of sand) on their bodies at any given time. This is why prevention of RWIs involves staying away from the water after you have a diarrheal illness and maintaining good hygiene.
More serious and potentially fatal causes of RWI include the amoeba Naegleria fowleri and the bacteria Legionella and Vibrio. These infections may involve loss of appetite, fever, confusion, lethargy, and weight loss as signs of severe disease. Vibrio is a particularly nasty organism for those with open wounds, diabetes, or chronic liver conditions. If cuts or sores appear to become intensely red, swollen, or painful after exposure to the water, an infection is likely. Even non-living cyanotoxins in the water from blue-green algal blooms can cause upset stomach, cough, or rash. Ear or eye pain are also frequent symptoms of RWI.
If you suspect that you may be sick from a waterborne illness, you should see your doctor and they will relay this information to public health authorities to prevent further exposures, along with treating your illness.
Thankfully there are a number of ways known to help avoid “dampening” your fun with Recreational Water Illnesses, including:
- Avoid fresh or brackish water activities when the water temperature is high (greater than 68o F) and the water level is low; these are prime conditions for problematic germs to grow.
- Do not swim in waters that are murky or have an odor. Do not swim in waters where you see a blue-green algal bloom.
- Heed swimming warnings posted around natural waterways.
- Avoid swallowing water that is intended for swimming; keep water out of your mouth as much as possible.
- Dry ears thoroughly after swimming.
- Cover any wounds with waterproof bandages; if you have had recent surgery or a piercing, avoid swimming.
- Shower after swimming.
To help keep the water clean for others:
- Shower before swimming.
- Wait for two weeks after any diarrhea has ended to go swimming.
- Wash your hands after using the bathroom or helping children with hygiene.
- Wash your hands before eating; if you have only hand sanitizer, be sure that hands are free from sand or grime before using.
- Change children in diapers frequently and take older children for frequent bathroom breaks during water activities (about every hour).
Allen Perkins and Marirose Trimmier, “Recreational Waterborne Illnesses: Recognition, Treatment, and Prevention,” American Family Physician, no. 9 (2017): 95.
Centers for Disease Control and Prevention, “Illness and Symptoms: Cyanobacteria in Fresh Water,” April 6, 2021.
Centers for Disease Control and Prevention, “Recreational Water Illnesses,” June 4, 2020.
Minnesota Department of Health, “Waterborne Illness.”