Health officials in North Carolina report that Lauren Seitz, an 18-year-old Ohio woman who died on Sunday after a rafting trip with her church earlier this month, had contracted primary amebic meningoencephalitis (PAM).

PAM is an almost always fatal infection caused by Naegleria fowleri, aka the “brain-eating amoeba." There's no denying it's terrifying. But here’s what experts who have encountered the parasite want you to know:

Infection is super rare

“[PAM] is highly lethal but very rare, even in areas where it’s endemic,” says Stanley Deresinski, MD, a clinical professor of medicine in the division of infectious diseases at Stanford University. Early symptoms, which start between one and nine days after exposure, are similar to those associated with meningitis, and include severe headache, fever, nausea, and vomiting.

According to the Centers for Disease Control and Prevention, a total of 138 infections were reported in the United States between 1962 and 2015. "Hundreds of millions of visits to swimming venues occur each year in the U.S. that result in 0-8 infections per year," the agency says. To put that in perspective, more than 3,500 people drown every year.

The amoeba loves heat

Naegleria fowleri is found in soil and warm freshwater environments like lakes, rivers, and hot springs. It thrives in summer, when air temperatures climb into the 80s and 90s and water temperatures reach the 70s.

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It’s found mostly in the south

The majority of PAM infections have occurred in southern states—Florida and Texas alone account for more than half of all U.S. cases. But as climate change heats the globe, Naegleria fowleri seems to have expanded its territory. Minnesota confirmed cases in both 2010 and 2012. “If temperatures continue to rise, we could see this in areas farther north,” says Bobbi Pritt, MD, director of the Clinical Parasitology Laboratory in Mayo Clinic’s Department of Laboratory Medicine and Pathology. 

People are not the amoeba’s preferred habitat

While the parasite loves heat, it doesn’t necessarily love humans. “Naegleria fowleri are free-living organisms that would much rather remain in the environment than end up in a human. We’re a dead-end host, and not part of their life cycle,” says Dr. Pritt.

It comes in through our noses

We become infected not by swallowing contaminated water, but by allowing the water into our nostrils, explains Dr. Deresinski. The parasite enters the central nervous system via the olfactory nerve in the nose.

“In terms of the major risk, it’s submerging your head in warm, non-chlorinated fresh water,” he explains. “When I lived in Florida, I floated around in a lake all the time—but I never put my head underwater. The thing to avoid is situations that will clearly lead to water entering your nostrils.”

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Nose plugs are your best defense

If you’re going to be spending time in fresh water, blocking your nasal passages with pinched fingers (if you take a brief dip) or wearing a nose plug (if you’re going tubing, rafting, or swimming) will deny the parasite entry, full stop. “If I had a really good nose plug, I wouldn’t even think about [potential infection],” says Dr. Pritt.

It’s also important to avoid infection via devices like neti pots, which have been linked to PAM in a few recent cases. “The safest approach is to boil water before you use it [to irrigate your nasal passages], and to clean your neti pot with water that’s been boiled,” she says.

Bottom line

The odds of your contracting this horrible infection are incredibly small. By making a habit of a few common-sense precautions, you can render them infinitesimal.