Lake water, a common setting for summer recreation, can pose health risks, particularly if the water is visibly polluted, stagnant, or accidentally swallowed. Illnesses contracted from natural bodies of water like lakes are broadly termed Recreational Water Illnesses (RWIs). These conditions are caused by exposure to germs and chemicals present in the water, which can enter the body through swallowing, breathing in fine mists, or direct contact with the skin, eyes, or ears.
The Primary Sources of Contamination
The most common cause of sickness in lake water involves pathogenic microbes, typically introduced through fecal contamination. These microscopic organisms include bacteria, viruses, and parasites that thrive in untreated water. Common culprits are parasites like Cryptosporidium and Giardia, which are highly resistant to chlorine and can survive in water for extended periods.
These pathogens often enter lakes and rivers through agricultural runoff, failing septic systems, sewage overflows, and storm water runoff, especially after heavy rains. The presence of bacteria such as E. coli indicates that human or animal waste may be in the water, raising the risk of contracting a diarrheal illness. Swallowing even a small amount of contaminated water can lead to infection.
A distinct source of illness is Harmful Algal Blooms (HABs), frequently caused by cyanobacteria, also known as blue-green algae. While most algae are harmless, cyanobacteria can produce potent toxins called cyanotoxins. These toxins can be dangerous to humans and animals. Exposure to these blooms can occur through skin contact, inhalation of water droplets, or swallowing the water.
How Illness Manifests
Contaminated lake water affects different bodily systems, with gastrointestinal issues being the most commonly reported. Ingesting contaminated water can lead to acute gastrointestinal illnesses, characterized by symptoms like watery diarrhea, vomiting, stomach cramps, and sometimes fever. Parasites like Giardia and Cryptosporidium are frequent causes of this type of illness, which can sometimes result in significant dehydration.
Lake water exposure can also result in dermatological and sensory infections. A common rash, known as “swimmer’s itch,” is an allergic reaction to parasites that burrow into the skin before quickly dying, resulting in small, itchy red pimples. Contaminated water can also cause outer ear infections, commonly called “swimmer’s ear,” when water remains trapped in the ear canal, allowing bacteria to multiply.
Infections are not limited to the surface of the body; contaminated water can also affect the respiratory system. Inhaling aerosolized water droplets from a lake, which can happen near fountains or during active water play, may lead to respiratory illnesses such as Pontiac fever. Additionally, contact with cyanotoxins from HABs can cause symptoms like eye and nose irritation, a sore throat, and a cough.
Reducing Risk and Seeking Medical Attention
Heeding public health warnings or beach closures related to water quality is a primary preventative measure. It is advisable to avoid swimming in lakes immediately after a heavy rain, as this causes contaminants from the surrounding land to wash into the water. Swimmers should also avoid swallowing the water, which is the main route of infection for gastrointestinal pathogens.
After swimming, showering with soap and water is recommended to wash off lingering microbes. Individuals should avoid swimming if they are currently experiencing diarrhea, as this can easily contaminate the water and infect others. Small children should be taken on frequent bathroom breaks to prevent accidental contamination.
While most RWIs are self-limiting, certain symptoms warrant immediate medical attention. Individuals should see a doctor if they experience bloody diarrhea, a high fever, or symptoms that persist for more than a few days. Vulnerable populations, including the elderly, young children, and those with weakened immune systems, face a higher risk of severe illness and should seek medical care sooner, especially if they suspect exposure to a harmful algal bloom.