Potentially Harmful Germs Found in Water

Potentially Harmful Germs Found in Water

The Hidden Hazards in Recreational Water

Swimming Pool

Underneath the shimmering surface of your favorite swimming pool, beach, or lake, potentially dangerous microorganisms may be lurking. These unseen hazards have the ability to turn a refreshing dip into a nasty infection. Dr. Stacey Rose, an associate professor of infectious diseases at Baylor College of Medicine, warns that “microorganisms thrive in every type of water, and infections will impact everyone differently.”

The Dangers in Shared Water Environments

Recreational swimming activities have been associated with outbreaks of various microorganisms, including Cryptosporidium, Legionella, norovirus, and Giardia. Individuals with compromised immune systems or open wounds should refrain from swimming in these shared water environments. Those with open wounds run the risk of shedding harmful bacteria, which can then be spread to others, resulting in conditions such as diarrhea, skin rashes, ear pain, cough, congestion, and eye pain.

It’s vital for people recovering from diarrhea to avoid swimming in public waters for at least two weeks. Dr. Rose explains that “you can shed microorganisms like norovirus or E. coli for several days, sometimes weeks after diarrhea has subsided.” Additional caution should be taken in bodies of water designed for babies and toddlers, as these often have higher-than-usual amounts of fecal matter, posing a higher risk of bacterial spread.

The Limits of Water Treatment

Pools and water parks typically treat their water with chlorine to eliminate harmful microorganisms. However, frequent use by multiple swimmers can introduce new microorganisms or increase the levels of those already present, thereby reducing the effectiveness of the chemical. Furthermore, certain microorganisms, such as Cryptosporidium, have shown resistance to chlorine, making them even harder to eradicate.

Freshwater and saltwater environments also harbor their own unique hazards. In freshwater, there is a rare but dangerous organism called Naegleria fowleri, commonly known as the brain-eating amoeba. Dr. Rose suggests pinching your nose when diving into freshwater to prevent water from directly entering your sinuses and potentially causing an infection.

Swimming in brackish water or the Gulf of Mexico can expose you to Vibrio vulnificus, especially if you have liver disease or other immune-compromising conditions. This bacterium poses the highest risk in such circumstances.

Preventive Measures

Dr. Rose recommends a few preventive tips to help minimize the risk of infection. After swimming, it’s important to rinse off with a shower to remove any lingering microorganisms. Consider purchasing test strips to measure chlorine levels in the water, empowering you to monitor the safety of the environment. If anything seems amiss, such as foul odors, discolored or cloudy water, or the presence of drainage pipes, it is wise to exercise caution and avoid swimming. Proper maintenance and cleaning schedules for personal pools are also essential before inviting others to swim.

In Dr. Rose’s words, “think of swimming hygiene as a two-way street—by taking the right precautions, you protect yourself and, in turn, protect others.”


While recreational water activities can be a source of great pleasure and relaxation, it’s crucial to be aware of the potential health risks that exist below the surface. By understanding the dangers posed by microorganisms and adopting preventive measures, such as proper hygiene, water testing, and cautious behavior, we can continue to enjoy these activities while safeguarding our health and the well-being of others.

Sources: – Baylor College of Medicine, news release, June 28, 2023MedicineNet Slideshow