Stephanie Stahl reports…

PHILADELPHIA (CBS) – A warning for people who swim in lakes and rivers, especially while vacationing in the south. A deadly, brain eating amoeba, called Naegleria fowleri, may be lurking in those waters. 3 On Your Side Health Reporter Stephanie Stahl has more.

This amoeba is a parasite that lives in fresh water and can infect a persons brain. It’s rare, striking only about 117 people in the last 50 years. But this month it’s taken two lives.

The amoeba infection killed 9-year-old Christian Strickland. A week after going to a fishing camp near his Richmond, Virginia home.

“The next morning he doesn’t want to get out of bed. He’s falling asleep in an instant, and he looks at me like he’s trying to figure out who I am,” said Amber Strickland, his mother.

It also happened to 16-year-old Courtney Nash in Florida, after swimming in a river. She died a week later.

The killer is a microscopic amoeba living in freshwater lakes, rivers, and hot springs.

“Unfortunately when people get into the water if they’re swimming they can potentially stir up the sediment and this amoeba essentially goes up the nose and then causes a severe brain infection,” said Dr. Michael Beach, Associated Director for Healthy Water at the Centers for Disease Control.

The amoeba infects people by attacking brain tissue and kills quickly, usually in one to 12 days.

Symptoms to look for include headaches, a stiff neck, and vomiting after being in fresh water. Experts say to prevent the problem, while swimming, hold your nose, wear a nose clip, don’t stir up the sediment, and avoid shallow, warm water.

“We think this is really related to water temperature. So you see it in the Southern tier states at the bottom of the United States,” said Dr. Beach.

Texas and Florida have the majority of these deadly infections. They are not contagious.

Doctors stress these illnesses are rare, and say bacteria in your backyard pool are much more likely to make you sick.

For more information on Naegleria Fowleri, visit: http://www.cdc.gov/parasites/naegleria/faqs.html