Brain-eating amoeba: How tiny killers ravage our nervous system

Our bodies fight off countless microscopic attackers all the time.

But one little intruder has earned a notorious reputation for bypassing our natural defenses, burrowing into our skulls and destroying our brains - almost always with fatal results.

Public-health officials and scientists across the South, including Florida, are on alert because of Naegleria fowleri, an amoeba that lives in freshwater and becomes active in the heat of the summer.

Infections are rare.

But with recent cases in Florida and Arkansas drawing attention to the killer amoeba, the Orlando Sentinel recently asked experts how N. fowleri attacks and what we can do to stay safe.

Q: What’s the best way to avoid infection?

A: The amoeba is found everywhere in fresh water, including lakes, rivers and hot springs, so the best way to reduce risk is to avoid such bodies of water. That’s especially true in Florida during the summer. The peak months for infections are July, August and September. Southern states have the most cases. Florida led the nation with 33 cases from 1962 to 2012, according to the Atlanta-based federal Centers for Disease Control and Prevention. Texas came in second with 31 cases during the same period.

Q: What should I do in fresh water?

A: If you can’t avoid fresh water, make sure to keep your head out of the water. Hold your nose shut or use nose clips. Avoid digging in or stirring up sediment. That could release more organisms to the surface and eventually into your body.

Q: How does it attack?

A: N. fowleri attaches to the cells that line the inside of our noses, also known as the “nasal mucosa,” according to Dr. Nicole M. Iovine, director of the Antimicrobial Management Program in the Division of Infectious Diseases & Global Medicine at the University of Florida.

Q: What happens next?

A: It produces toxic proteins that kill the mucosa cells, allowing it to invade deeper. It moves on its own, using two whiplike structures called flagella. Then it takes a ride along the olfactory nerve, which gives it a direct route into the brain.

Q: Why does it attack our nervous system?

A: Iovine said certain areas of the body aren’t as well protected as others. When N. fowleri gains access to the central nervous system, for example, it establishes infections before immune responses can kick in.

Q: Does the disease have a name?

A: Yes, it’s called primary amebic meningoencephalitis, or PAM. The rare disease is almost always fatal. Only two people in North America out of 128 have survived infection from 1962 to 2012. That doesn’t include an Arkansas girl this summer thought to be the third survivor.

Q: What are the symptoms?

A: The symptoms are sometimes misdiagnosed because they are similar to those of bacterial meningitis. The first stage of PAM includes severe headache, fever, nausea and vomiting. Second-stage symptoms include stiff neck, seizure, hallucinations and coma. Symptoms start one to seven days after exposure, and death follows one to 12 days after symptoms.

Q: What do we know about the current cases?

A: Zachary Reyna, 12, was infected while knee-boarding in a ditch near his LaBelle, Fla., home on Aug. 3. The child is being treated in Miami Children’s Hospital intensive-care unit. A 12-year-old girl from Arkansas, Kali Hardig, was infected a month ago after swimming in Willow Springs Water Park in Little Rock and has recovered.

Doctors have permission from the CDC to give Zachary a drug that worked for Kali. She is considered the third well-documented case of a person in North America surviving the infection since 1962.

Q: Why aren’t there more cases?

A: That’s unclear. There is a lot scientists don’t know.

“The effects of PAM on the individuals who contract the amoeba are tragic,” Carina Blackmore, Florida’s interim state epidemiologist, said in a statement. “The low number of infections makes it difficult to know why a few people have been infected compared to the millions of other people that used the same or similar waters across the U.S.”

Information from The Miami Herald and CDC was used in this report. For more information, go to or