Faith, medicine or ZMapp?

For Ebola survivors Dr. Kent Brantly and Nancy Writebol, the answer is clear.

I would say the Lord. His merciful, gracious hand saved me in a way that used people and medication and a drug that had not been released. I think all of those things have played into our recovery, Writebol told NBC News in an exclusive interview for the Friday NBC News Special "Saving Dr. Brantly: The Inside Story of a Medical Miracle.

The doctors who treated them have another idea and they think what theyve learned can save Ebola patients in Africa. What almost killed Brantly, they say, were irregular heart rhythms caused by whats called electrolyte imbalance the loss of minerals because of his constant, unending diarrhea.

The closest infectious disease we can compare it to is cholera, Dr. Bruce Ribner, who heads the special containment unit at Emory University Hospital in Atlanta where Writebol and Brantly were treated, told NBC News.

As with cholera, the constant vomiting and diarrhea pull all the fluids from the body, and with them sodium, potassium, magnesium and calcium the so-called electrolytes that help the cells in organs such as the heart, brain and kidneys to function.

Brantly was losing five to seven quarts a day of fluid, Ribner said.

The first night each time he got out of bed to go to the bathroom, he was getting weaker and weaker, said Crystal Johnson, one of the nurses who cared to Brantly and Writebol. He was febrile. He could barely stand. Every hour was tedious. We could not leave the room. We had to stay in our Tyvek suits and stay in the room.

It was water. It was just water coming out of him, added infectious diseases specialist Dr. Aneesh Mehta, another member of Emorys Ebola team.

And with every bout of diarrhea, Brantly was losing the electrolytes that make the heart beat regularly. He was having rhythm problems because his electrolytes were so out of balance, Ribner said.

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Faith, Medicine or ZMapp: What Cured The Ebola Patients?