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A Brevard County teen was hospitalized after an amoeba is believed to have infected her brain while she was swimming in a local river.

The young girl, identified in numerous reports as 16-year-old Courtney Nash, is currently listed in critical condition, officials said.

Barry Inman, an epidemiologist with the Brevard County Health Department, told CBS Tampa that the very rare infection, known as amoebic meningoencephalitis, has not yet been confirmed by the Centers for Disease Control, but that officials believe a positive test will be returned any day.

"We got a result from the hospital in Orlando and they did a spinal tap on her, and they looked on the cerebral spinal fluid and they saw the amoeba. So we're confident that this is a hospital that has some experience with this organism, and we're confident about what the diagnosis is," he said.

Inman said there are typically fewer than five cases a year in the entire country, and that only one person has survived the infection since the 1970s. Doctors treat it with anti-fungal medications and antibiotics.

According to the Orlando Sentinel, Florida's last confirmed case came in 2009.

"We have like one or two maybe a year. Sometimes we go a few years without having any cases in the United States, so it's rare when it occurs, but when it occurs it's not good," Inman said.

Amoebic meningoencephalitis occurs often during very hot weather and is contracted in stagnant freshwater. "The water, because of jumping or swimming or whatever may occur, has to go up the nose into the nasal passages, into the sinuses, and into the brain," Inman said. "In the brain you've got a lot of cerebral spinal fluid, you've got glucose, you've got protein, it's just the perfect environment to proliferate and grow."

Officials urge swimmers to avoid swimming in bodies of freshwater. Those who do should wear nose plugs or hold their nose when they jump or dive in.