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Second American aid worker with Ebola arrives in US

ATLANTA — An American aid worker infected with Ebola arrived Tuesday in Atlanta, becoming the second patient being given an experimental treatment that has never before been tested on humans.

Nancy Writebol, 59, traveled from Monrovia, Liberia, to Emory University Hospital, just downhill from the US Centers for Disease Control and Prevention. She arrived two days after Kent Brantly, a doctor with whom she had worked in Liberia and who also contracted Ebola, showed up for treatment.

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The differences were stark in how they went from the ambulance to Emory, which has a highly specialized isolation unit. While Brantly, 33, was able to walk with assistance into the hospital, Writebol — covered from head to toe in a protective suit — was wheeled in on a stretcher.

Still, the 59-year-old Writebol was described as weak but showing signs of improvement.

‘‘A week ago we were thinking about making funeral arrangements for Nancy,’’ her husband, David, said in a statement read by the president of SIM USA, the aid group with which she was working in Liberia. ‘‘Now we have a real reason to be hopeful.’’

Brantly and Writebol were both infected despite taking precautions as they treated Ebola patients in West Africa, where the virus has been spreading faster than governments can contain it, killing nearly 900 people so far.

Their treatment, called ZMapp, was developed with US military funding by a San Diego company, using antibodies harvested from lab animals that had been injected with parts of the Ebola virus. Tobacco plants in Kentucky are being used to make the treatment.

It’s impossible to know whether the drug saved these workers, CDC Director Tom Frieden emphasized. ‘‘Every medicine has risks and benefits,’’ he said to reporters at a health symposium in Kentucky. ‘‘Until we do a study, we don’t know if it helps, if it hurts, or if it doesn’t make any difference.’’

If the treatment works, it could create pressure to speed through testing and production to help contain the disease in Africa.

There is no vaccine or specific treatment for Ebola, but several are under development, including ZMapp, made by Mapp Biopharmaceutical Inc. It works by boosting the immune system’s efforts to fight the virus. The US Defense Threat Reduction Agency announced last month that it is providing more funding to speed the drug’s development.

Brantly and Writebol had been working at a missionary clinic outside Liberia’s capital.

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