Scary Diseases You Can Catch While Swimming



There’s a disease that infects more than 200 million people a year worldwide — and you’ve probably never heard of it.

It’s schistosomiasis, a condition that occurs when humans come in contact with a certain type of freshwater snail carrying a dangerous parasite. “In terms of impact, this disease is second only to malaria as the most devastating parasitic disease,” the U.S. Centers for Disease Control and Prevention states on its website (though the particular parasite that infects humans is not found in the U.S.)

Individuals contract the illness, which causes rash, fever and muscle aches (that can persist for years if left untreated) through skin contact. The water is infected when sick people urinate or defecate in freshwater supplies.

Schistosomiasis can be cured, but some waterborne illnesses — both in the United States and around the world — cannot. And water doesn’t have to look dirty to be contaminated, either — just ask the hundreds of people sickened by a suspected norovirus after swimming in a Washington state lake earlier this summer.

‘Flesh-Eating Bacteria’

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Vibrio vulnificus, commonly known as flesh-eating bacteria, can lurk in warm saltwater. It’s rare — between 1988 and 2006, just more than 900 infections were recorded in Gulf Coast states — but it is also underreported, according to the CDC.

Earlier this summer, Florida health officials issued warnings about the bacteria after 10 people died (with 32 total sickened) after entering water off the Florida coast. Raw shellfish containing the bacteria can also transmit illness to humans.

Although it’s commonly known as flesh-eating bacteria, vibrio vulnificus is not technically flesh-eating, a term reserved only for bacteria classified as group A strep. Instead, vibrio vulnicius causes internal damage and “skin lesions that may appear similar to the skin damage caused by strep A,” Rajal Mody, a medical epidemiologist in the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, told CNN.

The bacteria typically enters the body through open scrapes, so swimmers with open cuts, scrapes or blisters should not go into the water. Those with compromised immune systems risk the worst complications from the infection.

Brain-Eating Ameba

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Naegleria fowleri is a microscopic ameba that can cause a rare, deadly infection in the brain called primary amebia meningoencephalitis (PAM). The ameba enters the human body through the nose where it attacks the brain, almost always ending in death.

It’s found in warm freshwater, such as lakes, rivers and hot springs, though it occasionally makes its way into municipal water supplies. PAM infections are incredibly rare — 34 cases have been recorded in the past 10 years with only one survivor.

The infections are mostly likely to occur in summer in the South where water is warmer year-around. Although, naegleria fowleri is becoming more common in northern states, including Minnesota.

Diarrhea and Other Stomach Symptoms

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The most common recreational water illness in the U.S. is diarrhea caused by parasites, such as Cryptosporidium and Giardia intestinalis, in recreational water, or Giardia intestinalis in drinking water. Some of these parasites are found in fecal matter, so they spread when fecal-contaminated water is consumed.

In the U.S., contact with sickening parasites and bacteria not only in lakes and ponds, but also in swimming pools. Last year, an incredible 58 percent of pool filters the CDC surveyed were found to contain E. coli, bacteria in human feces. Fifty-nine percent of filters sampled contained pseudomonas aeruginosa, which can cause skin and ear infections, according to the CDC.


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Recreating in a poorly maintained hot tub can results in contact with legionella, the bacteria that causes legionnaires’ disease and Pontiac fever, a milder form of the infection.

Legionella can also living in drinking water, and other warm water reservoirs, such as hot water tanks and large plumbing systems. Most people who come in contact with the bacteria won’t get sick, but others develop cough, shortness of breath, high fever, aches and more. Often, patients require hospitalization though they typically recover after antibiotics.


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A common viral illness acquired in freshwater, echovirus often results in pink eye, rashes, sore throat and the common cold. There’s no specific treatment; the human body almost always fights off the virus on its own.

In water, echovirus outbreaks most often occur in swimming pools, according to a review published in Applied Microbiology. The second-most outbreaks occurred in lakes or ponds. The common cause of echovirus infection from water is contaminated feces.