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When the weather’s hot, nothing beats heading to the nearest pool, lake or river to cool off. But as the temperature soars, so does the risk of illness caused by contaminated water.

Germs found in contaminated water can cause recreational water illness (RWI).

Swimmers and bathers most often become sick when they swallow contaminated water. The germs can come from swimming or bathing in any body of water from swimming pools, hot tubs and water parks to lakes, rivers and oceans.

Diarrhea, the most common illness, is often caused by swallowing water contaminated with Cryptosporidium or “Crypto” for short. Although you may be unaware you’ve swallowed contaminated water, most people accidentally swallow about an ounce of water each hour while swimming. The risk for illness increases when you swim with your head and mouth submerged.

Crypto is often found in rivers and lakes and can easily be passed to swimming pools, spas and other public facilities. Since Crypto can be found in even crystal clear rivers and streams, drinking even a small amount of water is risky.

If that person gets infected and then goes swimming in a pool or spa, they can easily pass the germs to other swimmers. To make matters worse, Crypto is resistant to chlorine, the main chemical used to disinfect swimming pools and spas. It can survive for days even in properly chlorinated pools

In 2013, the number of Crypto cases in Montana doubled from the previous year, from 60 cases to 120 cases.

In Yellowstone County, those cases shot up from three cases in 2012 to 39 cases in 2013, nearly one third of the cases in the entire state. The cases in Yellowstone County seemed linked to several different pools and an area stream.

Swimming, like other sports, involves a certain amount of risk. As the local public health agency, RiverStone Health tries to minimize that risk by conducting inspections of the 111 licensed indoor and outdoor pools and spas in Yellowstone County. The inspections focus on safety, water chemistry, recirculation and filtration equipment, and proper training of pool and spa operators.

After the spike in Crypto cases late last summer, RiverStone Health contacted pool operators to provide information on Crypto prevention. The best technique to get rid of Crypto in a pool is hyperchlorination, dramatically raising chlorine levels to kill the germs and then allowing the chlorine concentration to return to a level that is safe for swimmers and within public health regulations. Fortunately, last summer’s spike in Crypto cases came in late August, close to the end of the outdoor swimming season. Avoiding a similar outbreak this summer will take vigilance. Pool operators can do their part, but swimmers must shoulder some of the responsibility for keeping water safe and minimizing everyone’s risk.

The best — and most often overlooked — preventive measures are:

Wash hands frequently

Take a shower before entering a pool or a hot tub.

Avoid swallowing water from pools and rivers, lakes and streams.

The germs that cause Crypto and other recreational water illnesses can be found on the body of a person who is infected or is a carrier. Most of the pathogens are found in feces. Even trace amounts can cause harm. Taking a shower significantly reduces the amount of germs a person might introduce into the pool or spa. If people know they are contagious, or have diarrhea, they should stay out of the water.

Wading pools, and pools designed for toddlers, are at higher risk because children may not be fully toilet trained. If your child uses swim diapers, change them often and use a designated diaper changing area away from the swimming area. Be sure to wash your hands and your child’s hands often, especially after using the restroom or changing diapers.

Before entering the water, take a moment to observe your surroundings. Do not get into a pool if the water is cloudy or has poor clarity. The main drain should be visible and clearly defined. Report any unusual conditions to the pool operator.

Being aware of the risks associated with swimming and other water sports, and taking steps to reduce those risks, reduces the chance of contracting a recreational water illness.

Josh Juarez is the lead Registered Sanitarian with Environmental Health Services at RiverStone Health. He can be reached at 406-256-2770 or


Managing editor at The Billings Gazette.