Ebola-infected missionary describes her battle with the deadly virus

Smiling and appearing robustly healthy, a U.S. missionary infected with Ebola while working in Liberia on Wednesday shared publicly her battle with the deadly virus for the first time.

Nancy Writebol, 59, of Charlotte, North Carolina, has been recovering in an undisclosed location since her release last month from an Atlanta hospital that also treated another missionary who contracted the often lethal virus.

She told reporters there were mornings when she woke up and thought with surprise, "I'm alive."

"I thought whether I live or whether I die, it's going to be okay. It’s going to be okay," she said, speaking at times through tears about her recovery at the Charlotte headquarters of the Christian organization that she worked with, SIM USA.

Still, "there were many times when I thought, 'I don’t think I am going to make it any more," she told reporters at the group's Charlotte headquarters. "There were some very, very dark days."

On Tuesday, SIM USA said another U.S. doctor involved with its mission in Liberia had contracted the disease. The group, which has not disclosed the physician's name, is expected to provide additional detail on Wednesday and has said the physician is doing well and in good spirits.

Writebol's account of her illness comes as global health officials warned that the most severe Ebola outbreak in history appears to be worsening.

The outbreak has infected more than 3,000 people and killed some 1,550 since it was first detected early this year in West Africa, according to the World Health Organization.

For Writebol, her recovery involved a dramatic medical journey that drew international attention as well as scrutiny over treatment options.

After contracting the disease in Liberia in July, she was flown back to the United States to receive care in an isolation unit at Emory University Hospital in Atlanta.

She was also one of a few patients to receive an experimental treatment, Mapp Biopharmaceutical Inc's ZMapp, although doctors at Emory said they could not determine whether it made a difference in her recovery.

During the course of her illness, she endured "dark hours of fear and loneliness," her husband has said, leaving the hospital virus-free, but in weakened condition.

A mother of two, Writebol has been recuperating in an undisclosed location with her husband, fellow missionary David Writebol, who was also in Liberia but developed no symptoms.

She was treated at Emory with another U.S. missionary, Dr. Kent Brantly, a Texas doctor who also received ZMapp and was also released last month.

Brantly, who worked with another missionary group called Samaritan's Purse, this week said he felt like he was going to die during the throes of the illness but somehow recovered.

"I don’t think there is anything special about me that made God save my life," he told NBC News in an interview, which aired late Tuesday and early Wednesday. "I survived. That is not to say that for everybody else who died God was absent."