NEW YORK (AP) — Plans are underway to bring back the two American aid workers sick with Ebola from Africa.A small private jet based in Atlanta has been dispatched to Liberia where the two Americans work for missionary groups. Officials say the jet is outfitted with a special, portable tent designed for transporting patients with highly infectious diseases.The U.S. State Department and the Centers for Disease Control and Prevention are helping to arrange the evacuation."The safety and security of U.S. citizens is our paramount concern," said the State Department spokeswoman Marie Harf, in a statement released Friday morning. "Every precaution is being taken to move the patients safely and securely."The two Americans — Dr. Kent Brantly and Nancy Writebol — are in serious condition and were still in Liberia on Friday, said the charity Samaritan's Purse. Their transfer to the U.S. should be completed by early next week, the North Carolina-based group said.Brantly, who works for Samaritan's Purse, treated Ebola patients at a Liberia hospital. Writebol also worked at the hospital for another U.S. mission group called SIM.An administrator for the now closed hospital, Dr. Jerry Brown, however, said the two Americans were to leave Liberia on Friday. He did not know how they were being transported or where they were headed.At least one of the Americans is expected to be treated in the U.S. at Atlanta's Emory University Hospital, which has a special isolation unit. Emory said Thursday that it expected the patient to arrive "within the next several days."The hospital declined to identify the patient, citing privacy laws. The private jet can only accommodate one patient at a time.The Emory solation unit is one of about four around the country for testing and treating people who may have been exposed to very dangerous viruses, said Dr. Eileen Farnon, a Temple University doctor who formerly worked at the CDC and led teams investigating past Ebola outbreaks in Africa.The current outbreak in the West African countries of Liberia, Guinea and Sierra Leone has killed more than 700 people.___AP Medical Writer Marilynn Marchione in Milwaukee and Emily Schmall in Fort Worth, Texas, contributed to this report.Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.