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Naegleria fowleri, also known as a brain-eating amoeba, seen under a microscope. (Photo: Centers for Disease Control and Prevention)

Naegleria fowleri, also known as a brain-eating amoeba, seen under a microscope. (Photo: Centers for Disease Control and Prevention)

BISHOP, Calif. — A 21-year-old woman’s sudden death is being blamed on a brain-eating amoeba she likely contracted while swimming, health officials in California said Thursday.

The victim, whose name has not been released, took a nap on June 16 and woke up with a headache, nausea and vomiting, according to the Inyo County Health Department.

Those symptoms stuck around into the next day, prompting her to go to the emergency room where she was diagnosed with meningitis, the county’s health officer said. But her health only became worse and she was flown to a hospital in Reno, Nevada, where she went into cardiac arrest and died.

Testing performed by the Centers for Disease Control and Prevention (CDC) in Atlanta came back positive for evidence of the amoeba known as Naegleria fowleri.

Public health officials said the woman likely contracted the amoeba “on private property that is only used by family and friends.” They don’t believe there is a risk to the general public and there has never been a case of human-to-human transmission.

Infections from Naegleria fowleri usually happen while swimming, when the patient gets contaminated water inside their nose. It is not spread by drinking water, public health officials said.

The amoeba moves to the brain along a nerve in the patient’s nose then wiggles through a bony plate in the skull called the cribiform plate. From there, it has access to the patient’s brain, which it begins to destroy.

Infections from this amoeba — which live in the bottom layer of warm bodies of water, and thrive when temperatures are high and water levels are low — are extremely rare, with 133 cases reported in the U.S. during the last 53 years. That’s about 3 cases per year, on average, with most of those infections happening in Texas and Florida.

“The relative risk is extremely low, and yet the stakes are high because the chance of dying when infected is almost 100 percent,” said Dr. Richard O. Johnson, Inyo County Public Health officer.

Symptoms start within days of exposure and include headache, fever, nausea, vomiting and stiff neck, health officials said.

The disease progresses rapidly and manifests itself in symptoms like confusion, seizures and hallucinations. Within three to seven days, a patient is usually killed by the invasive amoeba.

Most cases — 75 percent — have been associated with swimming in warm freshwater lakes and rivers, but some uncommon sources of infection include slip-n-slide, poorly maintained swimming pools, or a neti pot used for nasal cleaning or irrigation.

Health officials emphasized that there have been “no evident cases” of amoeba contamination in the U.S. in well-maintained, properly treated swimming pools or hot springs. The best way to protect yourself is to stay away from warm, untreated or poorly treated water, according to the CDC.

Other ways to protect yourself include:

  • Keeping your head above water in untreated hot springs or other thermally heated bodies of water, and during activities where water is forced up the nose, like water sports and diving.
  • Holding your nose shut or wear nose clips when swimming in warm, untreated freshwater.
  • Avoiding digging in or stirring up sediment in shallow, warm freshwater areas, where the amoeba may live.
  • Avoiding water-related activities in warm freshwater during periods of high temperature and low water levels.
  • Avoiding swimming in polluted water or unchlorinated swimming pools.
  • If using a neti pot for nasal cleansing or irrigation, use only filtered or boiled water.