A 24-year-old woman who fell from a homemade zip line has lost her leg and remains in critical condition after a rare flesh-eating infection fed on her wound. She will also lose her fingers in the next phase of surgery to save her life. A doctor has said she was in a "perfect storm" for the bacteria to thrive.

Aimee Copeland, a U.S. university student, fell from a zipline on May 1 and got wounded from the fall. While her wound seemed to have healed from the outside, she continued to feel terrible pain. Her doctor then found out she was battling a rare flesh-eating bacterial infection called necrotizing fasciitis. Her leg was amputated on May 6.

Aeromonas hydrophila is the name of the bacteria that triggers necrotizing fasciitis. It thrives in warm climates and fresh water. The medical journal Clinical Microbiology said Aeromonas rarely causes flesh-eating infection, but when it does, the infection is known to be fatal over 60 percent of the time.

"This was a perfect storm," said ABC News chief health and medical editor Dr. Richard Besser.

"She had an injury to her leg, she was exposed to water then had this germ, and she was one of those people where the germ just took off."

Aimee's father, Andy Copeland, has been updating his blog about her daughter's tragedy. He wrote:

"We take so much for granted in life, but I never imagined that one of my daughters would face this most unlikely of situations."

In an interview with the media, Dr William Schaffner of Vanderbilt University Medical School said necrotizing fasciitis was often quite subtle in its early stages.

Mr Copeland further wrote in his blog that he has not yet told Aimee about the extent of her condition.

"She will learn about the loss of her beautiful leg. She will discover that her hands lack the dexterity and tactile response she has known all her life... How would you respond in such a situation? I think that moment will be one of horror and depression for Aimee," Mr Copeland wrote.

In the next stage of operations, doctors said Aimee will also lose her fingers, but surgeons intend to save the palms of her hands in order for her to use prosthetics someday.

On NBC's Today show, Mr Copeland had said her daughter has a strong will, and their family will take the aftermath of the tragedy one day at a time.