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• Posted July 4, 2023

What's in the Water? Maybe Germs That Could Harm You

Under the surface of your favorite swimming pool, beach and lakes, hazards too small to be seen by the naked eye may await.

And these bacteria, viruses and parasites can turn a refreshing plunge into a nasty infection.

"There's a variety of microorganisms that can make recreational activities in water less than fun,"said Dr. Stacey Rose, associate professor of infectious diseases at Baylor College of Medicine in Houston. "Microorganisms thrive in every type of water, and infections will impact everyone differently."

Recreational swimming has been linked to outbreaks of Cryptosporidium, Legionella, norovirus and Giardia.

Folks who have compromised immune systems or open wounds should not swim in these shared water environments. Those with open wounds could shed harmful bacteria and spread them to others. An infection can lead to diarrhea, skin rashes, ear pain, cough or congestion and eye pain.

People who have had diarrhea should avoid swimming in public waters for at least two weeks, Rose said.

"You can shed microorganisms like norovirus or E. coli for several days, sometimes weeks after diarrhea has subsided,"she said in a college news release. "Children who still wear diapers are at a high risk of spreading these bacteria, so bodies of water designed for babies and toddlers often have higher than usual amounts of fecal matter."

Pools and water parks treat their water with chlorine to kill these harmful microorganisms, but frequent use by multiple swimmers can introduce new microorganisms or increase levels of those already in the water. This makes the chemical less effective.

And some microorganisms, such as Cryptosporidium, are resistant even to chlorine.

In freshwater and salt water, other hazards exist. In freshwater, that includes Naegleria fowleri, or brain-eating amoeba. Fortunately, it is uncommon.

"A great prevention technique is pinching your nose closed when diving in to prevent water from going directly into your sinuses and infecting you,"Rose said.

Swimming in brackish water or in the Gulf of Mexico can put you in contact with Vibrio vulnificus. If you have liver disease or other immune-compromising conditions, you're at highest risk.

Rose offered some preventive tips. Rinse off with a shower after swimming. Buy test strips that analyze chlorine levels, so you can test the water yourself.

Stop if the environment gives you pause -- for example, you smell something foul in the water, see discolored or cloudy water or see drainage pipes close to or in the water. Follow proper maintenance and cleaning schedules for your own pools before inviting others to swim.

"Think of swimming hygiene as a two-way street -- by taking the right precautions, you protect yourself and in turn protect others,"Rose said.

More information

The U.S. Centers for Disease Control and Prevention has more on swimming-related illnesses.

SOURCE: Baylor College of Medicine, news release, June 28, 2023