A swimmer has been hospitalized with a rare brain-eating amoeba after visiting a lake in Iowa

• A Missouri resident has been hospitalized with a rare brain infection after swimming in Iowa.
• The brain-eating amoeba known as Naegleria fowleri thrives in warm lakes and rivers.
• The infection can escalate from headaches to coma in a matter of days, and is often fatal.

A rare brain-eating amoeba has sickened a Missouri resident who went swimming in Iowa. The individual is now in intensive care.

The swimmer had recently visited the Lake of Three Fires in Taylor County, Iowa, according to a news release by the Iowa Department of Health and Human Services. Testing is currently underway to confirm whether the amoeba is present in the lake. In the meantime, the beach has been shut down as a precaution, health officials said.

The amoeba known as Naegleria fowleri causes a severe, usually fatal brain infection while victims are swimming or diving in warm freshwater. People cannot become infected by swallowing contaminated water; the amoeba must enter through the nose to reach the brain.

The associated brain infection, called primary amebic meningoencephalitis, has a fatality rate of over 97%, according to the Centers for Disease Control and Prevention.

One CDC scientist told CBS News that N. fowleri is "the worst parasite in the world that we know of" because it is difficult to diagnose and infections progress quickly. Symptoms may appear within a few days of exposure, and people typically die of the infection one to 18 days after they get sick.

Early symptoms include severe headache, fever, nausea, and vomiting, according to the CDC. As the infection progresses, patients may experience stiffness in the neck, altered mental status, seizures, hallucinations, and coma.

The Missouri resident is currently being treated in the intensive care unit of a hospital, according to state health officials.

This may be the first infection in Iowa

A handful of cases have been reported in neighboring states, but this would be the first infection to occur in Iowa if testing confirms the exposure.

Missouri reported a single case of primary amebic meningoencephalitis in 1987, while nearby states Kansas and Minnesota have documented two cases each.

Since the CDC began tracking brain-eating amoeba infections in 1962, a total of 154 cases have been reported. Just four of those individuals survived the infection.

Most infections with N. fowleri occur in the southern US, since the amoeba thrives in warm water.

A Florida resident died from the brain-eating amoeba in August 2020. Local news later reported that the victim was a 13-year-old boy who had swam in a lake and visited a waterpark while on vacation in North Florida.

A month later, a 6-year-old boy died in Texas after playing at a local splash pad. Testing later revealed the amoeba was present in water at the splash pad and in a water hose at the boy's home.