FREETOWN, Sierra Leone — Security forces went house-to-house looking for Ebola patients and others exposed to the disease Thursday in Sierra Leone's capital as the death toll from the worst recorded outbreak in history surpassed 700 in West Africa.
U.S. health officials urged Americans not to travel to the three countries hardest hit by the medical crisis: Sierra Leone, Liberia and Guinea.
Two Americans are sick with Ebola in Liberia. Their colleagues said Thursday they were in "grave" but stable condition, and one of them was to receive an experimental serum.
"There was only enough for one person. Dr. (Kent) Brantly asked that it be given to Nancy Writebol," said Franklin Graham, president of Samaritan's Purse, an aid organization that has been working in Liberia during the Ebola crisis.
Brantly, though, did receive a unit of blood from a 14-year-old boy who had survived Ebola because of the doctor's care, Graham said in a statement.
"The young boy and his family wanted to be able to help the doctor who saved his life," he said.
Giving a survivor's blood to a patient might be aimed at seeing whether any antibodies the survivor made to the virus could help someone else fight off the infection. This approach has been tried in previous Ebola outbreaks with mixed results.
No further details were provided on the experimental treatment. There is currently no licensed drug or vaccine for Ebola, and patients can only be given supportive care to keep them hydrated. There are a handful of experimental drug and vaccine candidates for Ebola and while some have had promising results in animals including monkeys, none has been rigorously tested in humans.
Authorities in Sierra Leone are vowing to contain the disease's spread by quarantining all those at home who have refused to go to isolation centers. Many have kept relatives at home to pray for their survival instead of bringing them to clinics that have had a 60 percent fatality rate. Those in the throngs of death can bleed from their eyes, mouth and ears.
The disease has continued to spread through bodily fluids as sick people remain out in the community and cared for by relatives without protective gear. People have become ill from touching sick family members and in some cases from soiled linens.
The World Health Organization on Thursday reported 57 new deaths in recent days, almost half of which occurred in Liberia.
Liberia's president on Wednesday also instituted new measures aimed at halting the spread of Ebola, including shutting down schools and ordering most public servants to stay home from work.
"It could be helpful for the government to have powers to isolate and quarantine people and it's certainly better than what's been done so far," said Dr. Heinz Feldmann, chief of virology at U.S. National Institute of Allergy and Infectious Diseases. "Whether it works, we will have to wait and see."
Dr. Unni Krishnan, head of disaster preparedness and response for the aid group Plan International, said closing schools could help as they bring large number of children together, which can amplify infection rates.
"Door-to-door searches are not going to be easy," he said. "What will help is encouraging people to come forward when they see symptoms and seek medical help."
The U.S. Peace Corps also was evacuating hundreds of its volunteers in the affected countries. Two Peace Corps workers are under isolation outside the U.S. after having contact with a person who later died from the Ebola virus, a State Department official said.
In Moberly, Missouri, Liz Sosniecki said she got a call from her 25-year-old son, Dane, a Peace Corps volunteer in Liberia. He had not been exposed to Ebola and expressed disappointment about leaving just six weeks after he arrived.
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