2nd American aid worker with Ebola arrives in US

A second American aid worker infected with Ebola arrived Tuesday in Atlanta, where doctors will closely monitor the effect of an experimental drug she agreed to take even though its safety was never tested on humans.

Nancy Writebol arrived from Monrovia, Liberia, in a chartered jet at Dobbins Air Reserve Base and was then taken in an ambulance to Emory University Hospital, just downhill from the U.S. Centers for Disease Control and Prevention.

Writebol "shows signs of continued improvement," said Bruce Johnson, president of SIM USA, the aid group with which she was working. Johnson said he had spoken with her husband, David Writebol, about her condition.

"A week ago we were thinking about making funeral arrangements for Nancy," David Writebol said in a statement read by Johnson at a news conference. "Now we have a real reason to be hopeful."

Though she was wheeled from the ambulance in a stretcher, she is progressing, according to her husband. She was able to stand up and, with assistance, get on the plane in Liberia. One the flight, she ate some yogurt, her husband said.

Three days earlier, the first American aid worker diagnosed with the virus, arrived at Emory. Dr. Kent Brantly walked from an ambulance.

The two patients -- being treated in an isolation unit -- were 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.

And while family members said both Americans have been improving after the novel treatment, doctors at Emory have released no details about the experimental drug. Writebol's employer, the SIM charity, said Tuesday that she remains in serious but stable condition.

The treatment was developed with U.S. military funding by a San Diego company, using antibodies harvested from mice that had been injected with parts of the Ebola virus. Tobacco plants in Kentucky are being used to reproduce it.

It's impossible to know whether the drug saved these workers from the hemorrhagic fever killing as many as 80 percent of the people the virus is infecting in Africa. They could be recovering on their own, or for other reasons, including better medical care than many Africans get.

In remarks to reporters Tuesday at a health symposium in Kentucky, CDC Director Tom Frieden reiterated that experts aren't yet sure of the effect of the experimental drug. "Every medicine has risks and benefits," he said. "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 political pressure to speed through testing and production to help contain the disease in Africa. Dozens of African heads of state were meeting with President Barack Obama Tuesday at a summit in Washington. But it could take years before any treatment can be proven to be effective and safe, let alone mass produced.

Brantly, 33, and Writebol, 59, were working at a missionary clinic outside Liberia's capital. The world's largest Ebola outbreak has now spread to Guinea, Sierra Leone and Nigeria's capital of Lagos, where millions live in densely crowded conditions.

There is no vaccine or specific treatment for Ebola, but several are under development, including ZMapp, made by Mapp Biopharmaceutical Inc. of San Diego. It works by boosting the immune system's efforts to fight the virus.

The U.S. Defense Threat Reduction Agency announced July 22 that it is providing more funding to speed the drug's development, including a critical application with the Food and Drug Administration and the production of enough of the drug to carry out human trials.

Even if that process is successful, any wider use remains many months away. But when the Americans fell sick, the charity Brantly works for, Samaritan's Purse, didn't wait.

According to the National Institute of Allergy and Infectious Diseases, part of the U.S. National Institutes of Health, the Boone, North Carolina-based group contacted the CDC in Liberia to discuss various experimental treatments and were referred to an NIH scientist in Liberia.

That scientist referred them to Mapp Biopharmaceutical, but neither he nor NIH had any "official role in procuring, transporting, approving, or administering the experimental products," the government agency said in a statement.

FDA permission must be obtained before any experimental treatments in the United States, but other countries are beyond the FDA's authority, and these aid workers were first treated in Liberia. The FDA has declined to comment on their treatment.

The experimental drug was flown to Africa, and both patients got some before the long flight to Atlanta, on a plane that could carry only one of them at a time.

Ebola is spread by close contact with blood and other bodily fluids, and Writebol's duties included disinfecting doctors and nurses entering or leaving the Ebola treatment area. Her son, Jeremy Writebol, said he hopes her case "might help develop a cure and resources to help those who are suffering."

The virus is much less deadly when patients get top-flight care, experts say.

The CDC has been criticized for not objecting to the arrival of Ebola victims on U.S. soil, but Frieden has emphasized that there is no threat of an outbreak spreading in the United States.

Writebol and Brantly will be sealed off from anyone who isn't wearing protective gear. Dr. Bruce Ribner, who will be treating them, said their families can speak with them through a plate-glass window.

But Ribner said any modern U.S. hospital could safely treat these patients using standard infection-control procedures. At least five other deadly hemorrhagic fevers have been handled at U.S. hospitals lacking such sophisticated isolation units, experts have said.

Emory's unit, one of four in the country, was built in partnership with the CDC. In 2005 it handled patients with SARS, a viral respiratory illness that spreads when carriers cough or sneeze.