BOSTON -- A 35-year-old new mother is in critical condition Friday morning after contracting a flesh-eating bacteria.

The woman was diagnosed just days after she gave birth by Caesarean section at Emerson Hospital in Concord, Mass., Boston television station WCVB reported.

Three days later, she was taken to Massachusetts General Hospital for a disease known as necrotizing fasciitis.

Experts said that while the flesh-eating disease is a rare condition, it comes from the same bug that causes strep throat and ear infections.

"Let's say there's a wound in the abdomen, whether it's surgical or for some other injury, and the organism gets in. It likes to multiply along the planes of tissue. It has enzymes that loosen up those planes so that it can move along. And as it moves along, it produces these toxins that cause tissue damage and death," said Dr. Gerald Keusch, the associate dean for Global Health at Boston University.

Keusch said it's a rare condition, and it's only when the strep bug invades tissue that it poses a serious threat.

"Penicillin was the drug of choice for this infection, but you also have to aggressively open up the areas that were being infected and do something ... which is the removal of the damaged tissue surgically," Keusch said.

Keusch said there's no way of knowing how the Emerson patient contracted the bacteria. He said because it is widespread and common in the environment, generally living on a human host, it could have been present on the victim herself before infection.

If caught early the condition is often treatable, experts said, and it is not unusually contagious. If isolated properly it poses no elevated threat to the public.