Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Headline-Grabbing Brain-Eating Amoeba Exceedingly Rare

Dear Doctor: We live in Orlando, and last year a teenager here was infected with that brain-eating amoeba. Now we're reading that it's in the drinking water in Louisiana. How common is it? Should we be worried about an epidemic?

Dear Reader: There's nothing quite like the words "brain-eating amoeba" to get the news cycle humming. And the reassurance we're about to give you -- it is extremely, exceedingly rare -- is not necessarily the most attention-grabbing. But that's where we're going to begin.

Between 2007 and 2016, there have been just 40 cases of the so-called brain-eating amoeba reported in all of the United States, according to the Centers for Disease Control and Prevention. To put that into even clearer perspective, that's 40 cases in 10 years among 324 million people.

The microscopic creature that's been making headlines is called Naegleria fowleri. Trace amounts of it were discovered in two community water systems in southern Louisiana during routine testing last June. Customers of the affected water facilities were promptly alerted by the Louisiana Department of Health, and disinfection procedures were implemented.

So what is it?

Naegleria fowleri is a single-celled organism found throughout the world in warm freshwater, like lakes, streams, rivers, ponds and hot springs. It enters the body through the nose, typically when people accidentally inhale water while swimming or diving. The amoeba then travels through the nasal passages and enters the brain via the olfactory nerve. Once there, it begins to destroy brain tissues.

You can't become infected by drinking contaminated water, or by swimming in water that has been adequately chlorinated. There have been no known cases of transmission through water vapor, as during a shower or through a humidifier.

The majority of infections reported since 1962 have been in the southern U.S., with half of those in Florida and Texas. But infections have occurred as far north as Minnesota and as far west as Nevada and California. The specific disease the organism causes is called primary amebic meningoencephalitis, or PAM. It's diagnosed using specific laboratory tests that, because the disease is so rare, are not widely available.

Symptoms begin one to nine days after infection, and are divided into two stages. They're similar to those of bacterial meningitis, which adds a level of difficulty to an accurate diagnosis.

The first stage of the disease is marked by a severe headache in the front of the head, often with fever, nausea and vomiting. This is followed by stiffness in the neck, altered mental state, seizures and coma.

Although in most cases the disease is fatal, the Orlando teenager you're referring to survived. It is believed that a swift diagnosis -- the infection was identified within hours of the onset of symptoms -- was key to his beating the odds. So was aggressive treatment, which included an investigational drug, and cooling his body to well below normal body temperature, a process known as therapeutic hypothermia.

Unlike other survivors, who had permanent neurological damage, the Orlando teen recovered fully and is back in school. The hope is that early diagnosis and novel therapeutics may lead to higher survival rates in the future.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)