ATLANTA - Aimee Copeland, a Georgia grad student, is fighting for her life because of the flesh-eating bacteria that infected her after she gashed her leg in a river two weeks ago. One of her legs was amputated and her fingers will be too, her father says, because of the spreading infection.

She has a rare condition, called necrotizing fasciitis, in which marauding bacteria run rampant through tissue. Affected areas sometimes have to be surgically removed to save the patient's life.

HOW OFTEN DO PEOPLE GET THESE INFECTIONS?

The government estimates roughly 750 flesh-eating bacteria cases occur each year, usually caused by a type of strep germ.

However, Aimee Copeland's infection was caused by another type of bacteria, Aeromonas hydrophila. Those cases are even rarer. One expert knew of only a few reported over the past few decades.

DO MOST PEOPLE SURVIVE?

Yes, but about 1 in 5 people with the most common kind of flesh-eating strep bacteria die. There are few statistics on Aeromonas-caused cases like Copeland's.

HOW DOES SOMETHING LIKE THIS HAPPEN?

The germs that can cause flesh-eating disease are common in warm and brackish waters like ponds, lakes and streams. They are not a threat to most people. An infectious disease expert at Vanderbilt University, Dr. William Schaffner, said: "I could dive in that same stream, in the same place, and if I don't injure myself I'm going to be perfectly fine. It's not going to get on the surface of my skin and burrow in. It doesn't do that."

But a cut or gash — especially a deep one — opens the door for flesh-eating bacteria.

IS THERE ANYTHING YOU CAN DO TO AVOID SUCH AN INFECTION?

Prompt and thorough medical care should stop the infection before it spreads. A wound can look clean, but if it's sutured or stapled up too soon it can create the kind of oxygen-deprived environment that helps these bacteria multiply and spread internally. Once established, these rare infections can be tricky to diagnose and treat.

Also, Aeromonas is resistant to some common antibiotics that work against strep and other infections, so it's important that doctors use the best medicines.

ARE SOME PEOPLE MORE AT RISK?

Yes, people with weakened immune systems are. Copeland's family has not said whether she had some type of medical condition that could have made her more vulnerable and relatives could not be reached for comment Monday. Her doctors, meanwhile, have refused interviews.