Nancy Writebol, the second American missionary to contract Ebola while working in Liberia, arrived Tuesday at Georgia's Dobbins Air Reserve Base.
From there she was taken by ambulance to Emory University Hospital in Atlanta, where she'll be closely monitored.
Writebol is said to be showing noticeable improvement after receiving an experimental drug known as ZMapp. The drug, which has never been tested on humans, was used out of desperation.
"She was eating a little bit, able to take in fluid, so you know we're cautiously optimistic," her son, Jeremy, said.
Writebol's colleague and fellow American, Dr. Kent Brantly, is also getting stronger.
Brantly was given a dose of ZMapp and a unit of blood from an Ebola survivor, in the hope of providing antibodies the patient's immune system may have produced to fight the virus.
ZMapp is part of an ongoing research program backed by the U.S. government and military. It works by boosting the immune system and is made from antibodies produced by lab animals exposed to Ebola.
Dr. David Stevens, CEO of the Christian Medical and Dental Association, talked more about the Ebola virus and the work and faith of Dr. Kent Brantly:
There is still no known cure for the virus, and doctors remain hesitant to call ZMapp or any other treatment a success at this point.
Meanwhile, an Ebola outbreak continues to ravage three African countries. To date, the death toll is hovering close to 900.
Despite the risk, missionary doctors like Brantly continue to serve on the front lines.
"If you look back in history -- clear back into 260 A.D. when there was an epidemic in Italy -- 5 million people died of smallpox and Christian leaders at that time wrote about Christians out in the streets taking care of people, actually sacrificing their lives to take care of others," Dr. David Stevens, CEO of the Christian Medical and Dental Association, noted.
Health officials in the United States remain on high alert, with Centers for Disease Control and Prevention staff stationed at 20 U.S. airports and border crossings to evaluate passengers with possible symptoms of the deadly virus.
So far, no cases have been reported in the United States.
A New York hospital treated one patient with Ebola-like symptoms, but initial tests show it's unlikely he has the virus.