SATURDAY, May 24, 2014 (HealthDay News) — Taking a dip in the water can help refresh you on a hot day, but you need to protect yourself and your family from bacteria and parasites that can lurk in water, an infectious disease expert says.

“One of the worst offenders is the kiddie wading pool,” Dr. Christopher Ohl, professor of infectious diseases at Wake Forest Baptist Medical Center, said in a medical center news release.

“Warm, shallow water and kids in swim diapers (which don’t do a good job of containing feces) can create a perfect breeding ground for water-borne infections even though the water is chlorinated. The best way to prevent young children from getting sick is to keep them from swallowing that water,” he explained.

If your child has any type of gastrointestinal illness, you should keep the youngster out of pools or water parks for several days, said Ohl, who is also medical director of communicable diseases for the Forsyth County Health Department in North Carolina.

Here are his other tips for cooling off safely:

Try to avoid swallowing water when you’re in pools or at water parks. Never drink untreated water from springs and streams. It may look clean, but you need to remember that wild animals drink from those sources and relieve themselves at the same time.

Freshwater streams and lakes can contain leptospirosis, a type of bacteria found in mammals’ urine. This infection can cause fever, headache and muscle aches in people, but is usually treatable, Ohl said.

Another threat is a rare but deadly brain-eating amoeba called Naegleria fowleri. In order to reduce your risk, don’t jump feet-first into warm, stagnant ponds. Doing so can push water into the top of your nose, which gives the amoeba an opportunity to get into your brain.

Infections from bacteria and parasites are less of a problem in salt water, but you should stay out of the ocean if you have a cut or wound that could get infected. You also need to be alert for jellyfish.

“Most people don’t realize that the tentacles of some jellyfish, especially Portuguese man-of-war, can be 10 to 15 feet long, so keep a safe distance to keep from being stung,” Ohl said.

More information

The U.S. Centers for Disease Control and Prevention has more about Naegleria fowleri.