Beware of bacteria, amoebas in water before you jump in this summer

With summer beginning, many people planning to flock to their favorite swimming holes may also want to read up on bacteria warnings. 

The increased traffic at ponds, lakes and rivers means extra attention needs to be paid to bacteria that can be hazardous, such as E coli and cyanobacteria. 

At least 20 people reported E. coli infections after swimming in a Virginia lake around Memorial Day. In Massachusetts, more than half of the 22 beaches closed mid June were due to "bacteria exceedance." 

If you're going out for a swim, shower before and afterward and try not swallow the water, the National Institutes of Health advises. Wash your hands before you eat or drink after playing in recreational waters or in the sand.

People also shouldn't go to the bathroom in the water and should stay out if they've had diarrhea recently to protect others, the organization says.

Check for warning signs, talk to lifeguards, and do your homework by checking on specific beaches through state and local alert systems.

FILE - One of Min­ne­ap­olis’ most popu­lar lakes was shut down August 14, 2019 amid wor­ry that an E. coli out­break that sick­ened three chil­dren may be more wide­spread. (Photo by Elizabeth Flores/Star Tribune via Getty Images)

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Here's what to know about the most common concerns:

E. coli bacteria

E. coli bacteria are common in the intestines of people and animals, and most are relatively harmless. 

But human and animal stool can pollute water, including streams, rivers and lakes – even pools if proper treatment isn’t in place. 

Small doses of some strains - including just a mouthful of contaminated water – can cause a range of conditions, including urinary tract infection, cystitis, intestinal infection and vomiting, with the worst cases leading to life-threatening blood poisoning.


Cyanobacteria — also referred to as blue-green algae — are plant-like organisms that live in water. 

They can quickly grow out of control, or "bloom," and some produce toxins that make people and animals sick, according to the U.S. Centers for Disease Control and Prevention

They can look like foam, scum, mats, or paint on the surface of the water. They can also grow underneath the water.

Symptoms of cyanobacteria exposure can include skin irritation, stomach cramps, vomiting, nausea, diarrhea, fever, sore throat, headache, muscle and joint pain, mouth blisters, seizures, and acute liver damage.

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Brain-eating amoeba

Brain-eating amoeba, also known as Naegleria fowleri, is a single-celled organism that lives in soil and warm fresh water, such as lakes, rivers and hot springs, according to the CDC

It can cause a brain infection when water containing the amoeba goes up the nose. Only about three people in the United States get infected each year, but these infections are usually fatal.

Last year, an Arkansas resident died after being infected. State health officials concluded that the person was likely exposed to it at a country club's splash pad.

This story was reported from Detroit. The Associated Press contributed.