ATLANTA — A second American missionary stricken with Ebola is expected to fly Tuesday to the U.S. for treatment, following a colleague who was admitted over the weekend to Emory University Hospital’s infectious disease unit.

A Liberian official confirmed to The Associated Press plans for Nancy Writebol to depart with a medical evacuation team. The official, Information Minister Lewis Brown, said the evacuation flight was scheduled to leave West Africa between 1 a.m. and 1.30 a.m. local time Tuesday.

Writebol’s son, Jeremy Writebol of Wichita, Kansas, said his mother “is still struggling” but that “there seems to be improvement” and that the family is optimistic she will recover amid a spreading Ebola outbreak that has killed at least 729 people in Liberia, Guinea and Sierra Leone.

The Writebols’ mission team partner, Dr. Kent Brantly, also was improving Sunday after he was admitted to Emory’s quarantine unit a day earlier, according to a statement from his wife.