MDH: Since it's been hot, avoid going underwater or plug your nose when you're swimming

Conditions are right for a very rare brain-eating amoeba in Minnesota lakes, so officials want people to assume it's where they're swimming.
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Wayzata Beach, Lake Minnetonka

The Minnesota Department of Health (MDH) is warning swimmers that a "very rare" brain-eating amoeba may be present in Minnesota lakes. 

MDH Director Kris Ehresmann told reporters in the COVID-19 media call Friday that because it's been so warm in Minnesota since the start of July, swimmers should assume the rare amoeba called Naegleria fowleri is present in the state's lakes and rivers so they should take the proper precautions. 

Naegleria fowleri is an amoeba that's found around the world in warm freshwater and soil. Only in the past decade has the amoeba been found in the northern United States and, according to Ehresmann, typically only after prolonged stretches of hot weather (like Minnesota has been experiencing), which cause water temperatures to rise and water levels to drop.

The amoeba very rarely infects people, but when it does it happens while they're swimming or diving in warm lakes or rivers. It enters through a swimmer's nose and travels to their brain, where it destroys the brain tissue. It can cause a "very rare" but severe brain infection called primary amebic meningoencephalitis (PAM), which is often fatal, MDH's website states.

There have been two confirmed cases of infections caused by Naegleria fowleri in Minnesota, in 2010 and 2012, media reports from the time state. In both cases, the children, ages 7 and 9, swam in Stillwater's Lily Lake and later died.

There was a suspected infection in 2015 involving a 10-year-old boy who went swimming in Glenwood's Lake Minnewaska and then got sick and died, but it was determined his death was not caused by the rare amoeba.

Take precautions while swimming

The health department isn't telling people not to go swimming, but Ehresmann says swimmers can reduce their risk by keeping their heads out of the water and using nose clips or plugging their noses when going underwater. Swimmers should also avoid digging or stirring up the sediment at the bottom of the lake or river.

There is no rapid, standardized test to detect for Naegleria fowleri in water, which is why the health department recommends just assuming the very rare parasite is there and limiting the amount of water that goes up your nose to help reduce your risk of infection.

According to MDH's website, people can't get infected by swimming in a pool that has been properly cleaned and is maintained and disinfected. They also can't get it from drinking contaminated water. 

The brain infection the amoeba can cause cannot be spread from person to person.

Symptoms of the PAM infection typically start about five days after infection and they can be mild, but get worse quickly and can cause death within about five days. Initial symptoms may include a headache, fever, nausea and vomiting. Later symptoms can include a stiff neck, confusion, lack of attention, loss of balance, seizures and hallucinations.

MDH says people should seek medical care right away if they have a sudden fever, headache, stiff neck and vomiting, especially if they've been in warm freshwater within the past two weeks.

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