An experimental serum for treating Ebola arrived in Liberia, and a Samaritan's Purse doctor requested it be given to his colleague, according to a news release from Samaritan's Purse.

Dr. Kent Brantly with Samaritan's Purse and Nancy Writebol, who is from Charlotte, are in grave condition after contracting the serious disease in Liberia. Their conditions are stable, officials said. Samaritan's Purse said Brantly took a slight turn for the worse overnight.

An experimental serum arrived in the country Wednesday but there was only enough for one person.

"Dr. Brantly asked that it be given to Nancy Writebol," said Franklin Graham, president of Samaritan's Purse. "However, Dr. Brantly received a unit of blood from a 14-year-old boy who has survived Ebola because of Dr. Brantly's care. The young boy and his family wanted to be able to help the doctor that saved his life."

The safety of the staff is top priority for Samaritan's Purse and the organization is working to evacuate all but the most essential personnel to their home countries.

The evacuation should be completed by this weekend, according to the organization.

None of the evacuating staff is ill and the World Health Organization and the Centers for Disease Control and Prevention says that people are not contagious unless they begin showing symptoms.

Samaritan's Purse said it's taking precautions that exceed the standards recommended by the CDC.

CNN was reporting that U.S. government officials are in ongoing talks to bring them back from Africa, according to an administration official and a State Department source.