healthHealth and Medicine

This Will Make You Think Twice Before Getting Into A Pool This Summer


Look how happy they look. Little do they know... Halfpoint/Shutterstock

The weather is getting warmer and department stores have set up aggressively colorful swimwear displays, meaning pool season has officially begun.

And just in case you didn’t already have an innate wariness of getting in small containers of water that countless other people have soaked in, the US Centers for Disease Control (CDC) has released a cheery warning about the health hazards of public pools, hot tubs, and water parks, and how to avoid them.


The quick and dirty summary: Several common human pathogens thrive in warm, underchlorinated water. If you don’t want to be their next host, don’t drink the water, don’t let anyone in the water who has had recent diarrhea, and, where possible, test the water with your own chemical test strips before getting in.  

According to the article, posted on the CDC’s Morbidity and Mortality Weekly Report, between 2000 and 2014, contaminated recreational waters led to 493 reported disease outbreaks – instances where at least two people contracted similar illnesses. These events led to at least 27,219 infections, of which eight were deadly.

Hotel pools and hot tubs were the worst offenders.

Of the 363 outbreaks with a confirmed microorganism culprit, 58 percent were identified as Cryptosporidium, 16 percent were Legionella, and 13 percent were Pseudomonas. The remaining 13 percent were caused by a mix of less prevalent pathogens.


Cryptosporidium topping the list is not too surprising, as the microscopic parasite is transmitted in a dormant cyst form that is highly resistant to chlorine, bromine, and other pool chemicals; meaning even well-maintained waters may harbor it. Cryptosporidium will set up shop in the lungs if they are inhaled, but their reproductive life cycle depends on getting into the intestines through consumption.  Once it takes hold in the gut, the host experiences severe diarrhea that contains millions of new cysts, ready to lurk in the environment for a new host.

Even the residual fecal matter on a person’s backside contains disease-inducing levels of cysts, and the intestines will continue to shed Cryptosporidium after the symptoms resolve. For that reason, the CDC has previously recommended that adults and children who have experienced diarrhea should wait two weeks for getting into any public pool or tub.

CDC Morbidity and Mortality Weekly Report

Legionella is a bacterium that can cause a serious pneumonia-like illness called Legionnaire’s disease and a milder, flu-like disease called Pontiac fever when aerosolized water droplets are inhaled.

Pseudomonas, on the other hand, leads to unpleasant external infections. When it takes root on the skin, it causes a subtype of folliculitis called “hot tub rash”. The bacterium can also inflame the skin lining the ear canal, resulting in otitis externa, aka swimmer's ear.


Thankfully, both Legionella and Pseudomonas can both be killed by properly dosed water. But in bad news, the agency estimates that about 20 percent of public pools and hot tubs failed to maintain adequate levels of disinfectant.

Now stay safe, and don’t forget your sunscreen!


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