MONROVIA, Liberia (AP) — A special plane transporting the second American infected with Ebola has left Liberia’s capital en route to Atlanta.

An Associated Press reporter saw the four-vehicle convoy that arrived at Monrovia’s airport early Tuesday. The chartered plane took off at 1:12 a.m. local time.

This handout photo provided Friday, August, 1, 2014, by Emory University, shows the isolation room at Emory University Hospital set up to treat patients exposed to certain infectious diseases and where an American aid worker infected with the Ebola virus in Africa will be treated in Atlanta. (AP Photo/Emory University, Jack Kearse)

Nancy Writebol, a missionary from North Carolina, will be treated at the same Atlanta hospital where an American doctor with Ebola already has been taken.

Writebol’s son, Jeremy, said his mother “is still struggling” but that “there seems to be improvement.”

Police officers guard an entrance to Emory University Hospital after an ambulance arrived transporting an American that was infected with the Ebola virus, Saturday, Aug. 2, 2014, in Atlanta. (AP Photo/David Goldman)

The two Americans infected with Ebola are getting an experimental drug so novel it has never been tested for safety in humans

Ebola has killed at least 887 people in four West African countries.