- A 24 year-old contracted a rare case of necrotizing fasciitis after a zip line accident in Georgia on May 1.

- Doctors amputated most of Aimee Copeland's left leg and hands.

- Aeromonas hydrophila can be found in freshwater and brackish water environments, but is a rare way of contracting necrotizing fasciitis.

Aimee Copeland, a 24-year-old University of West Georgia graduate student, is breathing on her own today. It's a huge milestone in her continuing battle against a rare infection -- necrotizing fasciitis.

Copeland contracted the rare form of flesh-eating bacteria after a zip line accident over a river in Georgia on May 1.

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The germs that cause flesh-eating disease are common in warm and brackish waters like ponds, lakes and streams and rivers like the one that Copeland fell into when her zip line broke. The bacteria are not a threat to most people.

Swimmers sometimes come into contact with aeromonas hydrophila -- the type of bacteria Copeland is fighting.

If swallowed, your immune system will attempt to fight off gastrointestinal infections. You may experience some diarrhea -- but in most cases, says Dr. William Schaffner, president of the National Foundation for Infectious Diseases, you're perfectly fine after towelling off.

If you have an open wound, like Copeland's, the bacteria can enter the body and quickly reproduce. While the bacteria don't actually eat flesh, they attack skin and tissue by giving off toxins.

"It requires the perfect storm of circumstances," Schaffner. "It's unlikely to happen. Which is also scientists' way of saying we don't really know."

When someone is infected, the bacteria spreads quickly by hiding from the body's immune system, making it difficult to diagnose. It's one of the fastest spreading infections known, according to The National Necrotizing Fasciitis Foundation.

Treatment starts with antibiotics, and usually involves removal of the infected areas as well. In Copeland's case, her hands were endangering her recovery, her father wrote on Facebook: "As always, my decision was simple. Do whatever it takes to give us the best chance to save Aimee's life." The bacteria live in areas devoid of oxygen, so exposing the wounds to oxygen through surgery helps prevent their spread. But because the infection moves so fast, and because the bacteria thrive deep within the tissue, undetected, surgeons often have to go back in a second or third time, Schaffner says.

The struggle to save 24-year-old Aimee Copeland from necrotizing fasciitis has brought to life how devastating the disease can

In the most severe cases, organs can go into systemic shock, accompanied by respiratory and/or heart failure.

Jacqueline Roemmele, executive director of The National Necrotizing Fasciitis Foundation and NF survivor, says Copeland's case is typical in terms of diagnosis and treatment.

"It's pretty typical, and tragic," Roemmele said. "It's lightening fast, and drastic steps have to be taken quickly."

Roemmele, who calls herself the "grandma of flesh-eating disease" because she contracted the bacteria 18 years ago, says the most important thing to watch out for is pain out of proportion to the injury.

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"If you have a tiny cut on your leg, and 5-6 hours later your entire leg is killing you, and you have a fever, and your leg is turning red and swelling, don't wait," she says. "Get to a doctor."

Copeland's case is atypical, however, in that she contracted the bacteria through water, Roemmele says. Some have contracted the bacteria in shellfish, while shucking oysters, for example. And in a strikingly similar case to Copeland's, a Long Island woman contracted the bacteria last year on spring break while playing in the water.

"She almost lost her leg; as she went into surgery, she was told her leg would be amputated," Roemmele says. Instead, surgeons were able to remove only flesh, and she made it to her graduation ceremony two weeks after her skin grafts.

But most cases are caused by group A streptococcus bacteria that don't respond to antibiotics, the culprit of the common Strep throat; a mixed bacterial infection can also occur after surgery.

About 10,000 cases of group A streptococcus occur every year in the U.S. A few hundred cases of NF occur annually, Schaffner says, and about 20 percent of cases are fatal.

Although there's no specific method of prevention, Roemmele recommends keeping your immune system as healthy as possible.

"Give it the best shot you can by keeping healthy," she says.