Brain-Eating Amoeba Lurk in U.S. Lakes. But Should You Worry?

BY Jason Kane  August 22, 2011 at 3:07 PM EDT


Photo by Flickr user Toby Simkin.

Brain-eating amoeba, found in warm lakes, streams, and hot springs, are back.

Or more accurately, they never went away. Three people have died in recent weeks after attacks from a single-celled organism called Naegleria fowleri: A girl in Florida, a boy in Virginia and a 20-year-old man in Louisiana.

Could it be the start of a real-life version of a bad sci-fi flick? Probably not, according to infectious disease expert Dr. Roy Gulick of the Weill Cornell Medical College. Between one and eight people have been killed by the amoeba almost every year in the United States since it was first discovered in the mid-1960s.

That’s a pretty small number given that countless numbers of the amoeba that are floating in warm bodies of water nationwide, mostly in southern states. Each year, millions of Americans are exposed without the slightest repercussion.

“The illness itself is devastating, but the fact is that this is a very rare infection. It’s not a new infection, we’ve known about this for decades, and there’s no evidence that the number is increasing,” Gulick said. “If you compare it to the odds of having a traffic accident on your way to the lake or drowning in the lake, this is much smaller.”

For those unfortunate few, the outcome is almost always tragic. Within a week, the amoeba wreaks enough havoc to cause primary amoebic meningoencephalitis — a condition accompanied by intense headaches, fever, vomiting and a stiffening of the neck. Confusion, seizures, hallucinations and death usually follow.

From 2001 to 2010, only 32 people in the United States were infected — a far cry from the the 36,000 drowning deaths recorded in the 10-year span from 1996 and 2005, according to the CDC.

The freshwater killer doesn’t even like humans, Gulick said — it only attacks people when it’s forced up the nose. Once there, it travels through the olfactory nerve into the brain’s frontal lobe, where it feasts on brain cells and multiplies. But that’s only because the bacteria that it prefers in murky, warm water is nowhere to be found.

Swallowing it or coming into contact with it through empty cuts doesn’t appear to cause any harm whatsoever, said Jonathan Yoder, an epidemiologist for the Centers for Disease Control. And the amoeba also don’t appear to be present in chlorine-filled pools or saltwater bodies.

While it’s still unclear why some people are infected and so many remain unscathed, scientists guess that behavior probably has something to do with it — especially activities that propel water up the nose, like diving, splashing and roughousing.

About 80 percent of the cases are found in boys and men, and almost half are under 13.

There is no effective treatment at the moment, but CDC officials say several trials have been successful in the laboratory. Last week, the agency requested samples from Virginia water sources, hoping that a test might be developed to detect the amoeba. But even a systematic look at all the lakes in a given state wouldn’t do much good, Yoder said. Because the amoeba strikes so sporadically — and shifts location depending upon the temperature in a body of water — widespread testing might only instigate unnecessary panic if the amoeba is detected or complacency if it’s not.

“We think if you sample enough lakes and ponds in southern states, you’ll find it in many,” he said. “It’s about the decisions you make based upon that.”

Yoder’s advice: know the risks, make sure water isn’t jammed up your nose, and enjoy the warm weather.