You can get sick from swimming in pools, lakes, rivers, or the ocean; these ailments are collectively known as Recreational Water Illnesses (RWIs). RWIs are conditions spread by swallowing, breathing in mists or aerosols from, or having contact with water contaminated by germs or chemicals. Understanding the sources of contamination and the types of sicknesses that can occur is the first step toward minimizing your risk.
How Recreational Water Becomes Contaminated
The contamination of recreational water involves two main pathways: the introduction of biological pathogens and the buildup of chemical irritants. Biological contamination primarily stems from human and animal fecal matter, which introduces bacteria, viruses, and parasites. Even a small amount of feces on a swimmer’s body can wash off and contaminate a pool, especially with germs like the parasite Cryptosporidium, which is highly resistant to standard chlorine levels.
Organic substances such as sweat, urine, and dirt on swimmers’ bodies react with disinfectants like chlorine or bromine. This reaction reduces the amount of free disinfectant available to kill germs, allowing them to multiply. This process also generates chemical byproducts, like chloramines, which are irritants rather than protective disinfectants.
Natural water sources, like lakes and beaches, face contamination from agricultural runoff, sewage overflows, and storm water. These sources carry pathogens and excess nutrients, which can trigger harmful algal blooms, including cyanobacteria. These blooms produce toxins that can be hazardous to human health upon contact or ingestion. Elevated E. coli levels in natural waters often signal recent fecal contamination.
Distinct Categories of Swimming-Related Illnesses
The most frequently reported RWIs are gastrointestinal illnesses, which result from accidentally swallowing contaminated water. These infections are commonly caused by parasites such as Cryptosporidium and Giardia, along with bacteria like E. coli and viruses like Norovirus. Symptoms usually involve watery diarrhea, stomach cramps, nausea, and sometimes vomiting. Cryptosporidium is notorious for causing prolonged outbreaks because of its chlorine tolerance.
Dermal and skin infections occur through direct contact with contaminated water. Hot tub rash, caused by the bacterium Pseudomonas aeruginosa, manifests as an itchy, bumpy red rash or pus-filled blisters, thriving in poorly maintained, warm spa environments. In natural bodies of water, swimmer’s itch (cercarial dermatitis) is caused by microscopic parasites burrowing into the skin, causing tingling, burning, and small, itchy red bumps.
Respiratory and ear/eye infections are also transmitted through water exposure. Swimmer’s ear (otitis externa) is a bacterial infection of the outer ear canal that develops when trapped water creates a moist environment for germ growth. More serious respiratory illnesses, such as Legionnaires’ disease, can be contracted by inhaling fine water mist or aerosols. This allows the Legionella bacteria, often generated by hot tubs, to reach the lungs.
Key Prevention Guidelines for Water Safety
Preventing the spread of RWIs starts with adopting effective personal hygiene practices before entering the water. Taking a pre-swim shower removes dirt, sweat, and fecal matter, significantly reducing the introduction of germs and organic material into the water. It is also recommended to wash hands thoroughly with soap after using the restroom or changing a diaper, as hands are a common vector for transferring contaminants.
Behavioral changes while swimming are equally important for mitigating risk to yourself and others. Individuals who have experienced diarrhea should avoid swimming entirely for at least two weeks after symptoms resolve to prevent the spread of infectious germs like Cryptosporidium. Swimmers should also make a conscious effort to keep water out of their mouths and avoid swallowing it, which is the primary route of infection for gastrointestinal illnesses.
Environmental awareness is necessary, especially when using natural waters or public facilities. Before swimming at a beach or lake, check for local water quality reports or advisories regarding bacterial levels or harmful algal blooms. For pools, ensuring the water smells faintly of chlorine and does not have an overpowering chemical odor indicates proper water balance, as a strong smell signals the presence of irritating chloramines.