Kent Brantly, the American doctor infected with Ebola who was brought back from Africa and is being treated at a hospital in Atlanta, said Friday that his is getting better.

"I am growing stronger every day, and I thank God for His mercy as I have wrestled with this terrible disease," he said in a statement released by Samaritan's Purse, the international Christian humanitarian organization he was working for in Liberia.

Brantly was flown back to the U.S. last week from the African country in an air ambulance to be treated for the deadly virus, making him the first Ebola patient in the United States.

"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," the 33-year-old physician said.

Also hospitalized in isolation at Emory is Nancy Writebol, who was infected with Ebola at the same medical center where Brantly worked in Liberia, and who arrived in the U.S. last Tuesday.

"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," Brantly said.

The condition of both patients improved after they were given an experimental serum, never before used on humans, before traveling to the United States.

The Ebola outbreak affecting Liberia, Guinea, Sierra Leone and Nigeria, is the worst ever and to date has caused 961 deaths, according to figures of the World Health Organization. EFE