Dr. Kent Brantly, of Fort Worth, and missionary Nancy Writebol have each been given second doses of an experimental antibody serum designed to treat the deadly Ebola virus.
Brantly remains in stable condition at Emory University Hospital in Atlanta, NBC News is reporting, while the private jet used to ferry Brantly back to the U.S. has returned to Liberia for Writebol.
Brantly received a single dose of the serum before he left Liberia Saturday for Georgia. After landing in Atlanta, Brantly shocked many when he climbed out of an ambulance and walked into the university hospital Saturday.
Once in Atlanta, Brantly was given a second dose of the serum, NBC 5 has learned. Writebol has, to date, received two doses of the serum.
The doses are to be used as a set of three per patient. The vials of medication were originally going to be given to Writebol, but when Brantly took a turn for the worse last week the second dose was given to him, NBC News confirmed.
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There have been no official updates from the hospital, but by all appearances Brantly is showing signs of remarkable improvement compared to a week ago when doctors described his condition as "grave."
"Well it's encouraging. He seems to be improved from the reports we got earlier. Ebola can be deadly. But in people who are healthy the fatality rate may be lower than the ones we are usually quoting," said Dr. Tom Frieden with the Centers for Disease Control and Prevention.
Brantly was treating Ebola patients in Liberia when he began showing symptoms for the disease a week-and-a-half ago. During his treatment, he received a pint of blood from a 14-year-old boy who had recovered from the virus.
Emory, where Brantly already is quarantined, boasts one of the nation's most sophisticated infectious disease units. Patients are sealed off from anyone not in protective gear. Lab tests are conducted inside the unit, ensuring that viruses don't leave the quarantined area. Family members see and communicate with patients through barriers.
Brantly's wife released a statement Sunday saying she had gotten to see her husband, a physician with the international relief group Samaritan's Purse.
"Our family is rejoicing over Kent's safe arrival, and we are confident that he is receiving the very best care," Amber Brantly said.
Meanwhile, as Brantly is getting expert care at Emory University, the situation in Liberia continues to worsen. NBC 5 spoke via Skype with a health reporter in the capital of Monrovia.
"It's not getting better. It's getting worse. Yesterday evening, there was a mass burial of at least 25 persons including one Cameroonian medical doctor who was here providing aid like Dr. Brantly," said Liberian reporter Alaskai Johnson.
The death toll from the Ebola outbreak has reached 826 according to the World Health Organization.
The Associated Press contributed to this report.