Dr. Kent Brantly, the Fort Worth doctor who contracted Ebola doing aid work in West Africa, spoke Friday from his isolated Atlanta hospital room about the "horror" he witnessed and about his faith in God.

Brantly, who was volunteering with the charity Samaritan's Purse in Liberia amid the worst-ever outbreak of the deadly virus, has been improving steadily after being treated with an experimental drug.

"I am growing stronger every day, and I thank God for his mercy as I have wrestled with this terrible disease," Brantly said in a statement issued from the Emory University Hospital room where he is being treated in isolation.

He said he knew many victims of the outbreak, which has claimed nearly 1,000 lives in West Africa, were not so lucky.

"I held the hands of countless individuals as this terrible disease took their lives away from them," he said. "I witnessed the horror first-hand, and I can still remember every face and name."

Brantly was flown back to the United States last Saturday on a private jet designed to transport people with highly infectious diseases, after being given a single dose of the experimental drug ZMapp — a treatment that's still in development and hasn't been tested in humans.

He had become infected sometime in July, was officially diagnosed July 23 and fought the disease for more than a week in Liberia while his condition deteriorated before his return to the U.S.

Brantly then surprised millions when, after arriving in Georgia, he walked from an ambulance into Atlanta's Emory University Hospital amid reports that he was near death.

Since then, his condition has stabilized, and he is said to be doing better.

A second American aid worker, missionary Nancy Writebol, was also given a dose of ZMapp after contracting Ebola in Liberia. She was flown back to the United States on Tuesday and is also being treated in isolation at Emory University Hospital.

Writebol's husband, David, who remains in Liberia, told reporters Friday in a call organized by aid group SIM USA his wife appears to be improving. He said since his wife arrived in Atlanta, she has received another dose of ZMapp.

Few details have been released about the specific conditions of the patients. The aid groups referred questions to Emory, which has declined to comment, citing patient privacy.

Brantly, in his statement Friday, asked that people pray that he could continue to serve God in his work.

"As you continue to pray for Nancy and me, yes, please pray for our recovery. More importantly, pray that we would be faithful to God’s call on our lives in these new circumstances," he said.

Members at Brantly's church in Fort Worth continue to do just that.

"It was very encouraging to see his statement. His continued efforts to take the focus off himself and put it on the Lord and on others model Christ in a way that I think we should all aspire to," said Kent Smith, at Southside Church of Christ.

Emory, where Brantly and Writebol remain quarantined, boasts one of the nation's most sophisticated infectious disease units.

Patients are sealed off from anyone not in protective gear and lab tests are conducted inside the unit, ensuring that viruses don't leave the quarantined area, and patients can see and communicate with their family members through barriers.

Dr. Kent Brantly's statement:

I am writing this update from my isolation room at Emory University Hospital, where the doctors and nurses are providing the very best care possible. I am growing stronger every day, and I thank God for his mercy as I have wrestled with this terrible disease. I also want to extend my deep and sincere thanks to all of you who have been praying for my recovery as well as for Nancy and for the people of Liberia and West Africa. My wife Amber and I, along with our two children, did not move to Liberia for the specific purpose of fighting Ebola. We went to Liberia because we believe God called us to serve Him at ELWA Hospital. One thing I have learned is that following God often leads us to unexpected places. When Ebola spread into Liberia, my usual hospital work turned more and more toward treating the increasing number of Ebola patients. I held the hands of countless individuals as this terrible disease took their lives away from them. I witnessed the horror first-hand, and I can still remember every face and name. When I started feeling ill on that Wednesday morning, I immediately isolated myself until the test confirmed my diagnosis three days later. When the result was positive, I remember a deep sense of peace that was beyond all understanding. God was reminding me of what He had taught me years ago, that He will give me everything I need to be faithful to Him. Now it is two weeks later, and I am in a totally different setting. My focus, however, remains the same — to follow God. As you continue to pray for Nancy and me, yes, please pray for our recovery. More importantly, pray that we would be faithful to God’s call on our lives in these new circumstances.

NBC 5's Scott Gordon contributed to this report.