“Extremely strict procedures are in place for staff dispatched to Ebola affected countries before, during, and after their assignments,” said Sophie Delaunay, executive director of Doctors Without Borders in the U.S. “Despite the strict protocols, risk cannot be completely eliminated. However, close post-assignment monitoring allows for early detection of cases and for swift isolation and medical management.”

Spencer is the first of 700 expatriate staff with Doctors Without Borders, also known as Medecins Sans Frontieres, to develop symptoms after returning to their home country. Two MSF staff diagnosed in Africa were medically evacuated and treated in France and Norway.

In contrast to Doctors Without Borders, the aid group Samaritan’s Purse started quarantining all its volunteers upon their return from West Africa since Kent Brantly, a group-sponsored doctor, contracted Ebola in Liberia in August, said Franklin Graham, president of the North Carolina charitable group. About 30 volunteers have gone through quarantine since then at an undisclosed location within an hour of one of four U.S. hospitals specially trained to handle Ebola patients, he said.