One of the two American aid workers who contracted the Ebola virus in Liberia will receive a dose of experimental serum, after a doctor who also been infected insisted that she receive it instead of him.

The relief group Samaritan's Purse announced on Thursday that Nancy Writebol, a hygienist who was working to decontaminate those entering and leaving the ELWA Hospital in Liberia, would be the only one to receive an experimental Ebola serum, because there was not enough to provide two doses. Dr. Kent Brantly, who has been one of the leading physicians caring for patients in Liberia, came down with the disease last week and is now being praised by colleagues for requesting that the serum be given to Writebol first.

In a statement, President of Samaritan's Purse Franklin Graham outlined the next steps for both patients:

Yesterday, an experimental serum arrived in the country, but there was only enough for one person. Dr. Brantly asked that it be given to Nancy Writebol.

However, Dr. Brantly received a unit of blood from a 14-year-old boy who had 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.

Both Brantly and Writebol are listed in "stable, but grave condition." Their case has even reached the White House, which is investigating options to bring them back to the United States. In the meantime, Samaritan's Purse said it is in the process of evacuating all non-essential personnel, an effort that will be completed this weekend.

On Thursday, the CDC also issued a travel advisory for three nations where the virus has been found, Guinea, Sierra Leone, and Liberia, warning Americans to avoid all non-essential travel to the area.

The deadliest Ebola outbreak in history has now claimed more than 700 lives in West Africa, the WHO confirmed Thursday. Follow The Wire's timeline to learn how the disease managed to spread in less than five months.