WASHINGTON, Aug. 5 (Xinhua) -- The second American aid worker diagnosed with Ebola in West Africa was brought back to the United States for treatment Tuesday as international attention turned to the experimental drug both reportedly received as part of their treatment.
Nancy Writebol arrived in a private plane equipped with a unique containment unit at Dobbins Air Force Base near Atlanta Tuesday morning. The 59-year-old missionary from North Carolina was then transported by ambulance to Atlanta's Emory University Hospital, where her colleague, Kent Brantly, is also being treated.
Writebol is "very, very weak but shows continued, but slow improvement," said Bruce Johnson, president of SIM USA, the Christian charity she works for.
Johnson said Writebol's husband, David, who is still in Liberia, had expressed his gratitude for his wife's return to the United States.
"A week ago we were thinking about making funeral arrangements for Nancy," he quoted David as saying. "Now we have a real reason to be hopeful."
The hospital said in a statement the special isolation unit for the two patients was developed to treat patients who are exposed to certain serious infectious diseases.
"It is physically separate from other patient areas and has unique equipment and infrastructure that provide an extraordinarily high level of clinical isolation," it said. "As the Centers for Disease Control and Prevention (CDC) says, Ebola does not pose a significant risk to the U.S. public."
Writebol was serving on a joint team in Liberia with Brantly of Samaritan's Purse, an international relief organization, when they both contracted the virus.
Brantly, 33, was brought back by the same medical evacuation plane on Aug. 2 for treatment. Many experts were surprised to see him walk into the hospital. Writebol was carried in by stretcher.
Brantly's wife, Amber, said in a statement Tuesday that he was also recovering.
"I have been able to see Kent every day, and he continues to improve," she said. "I am also thrilled to see that Nancy arrived safely in Atlanta today ... we will walk through this recovery time together."
U.S. media reported both patients have been improving after they received a highly experimental antibody cocktail called ZMapp, created by San Diego-based Mapp Biopharmaceutical and LeafBio, as well as Defyrus Inc. from Toronto, Canada.
The three firms said in a statement that ZMapp, a mixture of three monoclonal antibodies, was first identified as a drug candidate in January and "has not yet been evaluated for safety in humans."
"As such, very little of the drug is currently available," the companies said. "Mapp and its partners are cooperating with appropriate government agencies to increase production as quickly as possible."
U.S. experts, however, are cautious, saying they are not sure if the two patients' recovery is the result of the ZMapp treatment.
"Since the product is still in an experimental stage, it is too early to know whether ZMapp is effective," the U.S. CDC said in a statement Tuesday. "It's important to note that the standard treatment for Ebola remains supportive therapy," including treating the Ebola patients for any complicating infections.
Some have raised the question of African sufferers' access to the experimental treatment, but the CDC reiterated that "the manufacturer reports that there is a very limited supply, so it cannot be purchased and is not available for general use."
According to the CDC, several companies are developing new Ebola treatments, but all are in the early stages of development.
The Ebola virus can kill up to 90 percent of those who become infected, and the fatality rate in the current epidemic is about 60 percent.
The outbreak, by far the largest in the nearly 40-year history of the disease, has affected 1,603 and killed 887 people this year in four western African countries -- Guinea, Liberia, Nigeria and Sierra Leone -- according to the World Health Organization.