Two Americans infected with Ebola are being treated at Emory University Hospital in Atlanta. "There is this report from Atlanta that this mixture of antibodies had a remarkable effect [on] a doctor who had been exposed," Davis said.
"The scientists who developed this treatment are from the United States," he said. "The treatment is experimental. It was obviously given as a last resort. Generally experimental treatments that haven't even been tried in humans go through much more testing before they are given."
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In Nigeria, a nurse there has died of Ebola. The country said it has five additional confirmed cases of the disease.
All six people had direct contact with a Liberian-American man who flew into Lagos last month after contracting the virus. He died of Ebola five days later.
Elsewhere, Saudi Arabia's Health Ministry says a man who was being tested for the Ebola virus and was in critical condition in an isolation ward has died.
The Health Ministry says the Saudi man died Wednesday morning in a hospital in Jiddah. He was hospitalized after showing symptoms of a viral hemorrhagic fever following a recent trip to Sierra Leone, where there has been an outbreak of Ebola.