An ambulance transporting Nancy Writebol, an American missionary stricken with Ebola, arrives at Emory University Hospital, Tuesday, Aug. 5, 2014, in Atlanta. Writebol is expected to be admitted to Emory University Hospital on Tuesday, where she will join another U.S. aid worker, Dr. Kent Brantly, in a special isolation unit. (AP Photo/David Goldman)

Aid group: American with Ebola weak but improving

The husband of the second American aid worker recently diagnosed with Ebola says his wife is weak but showing signs of improvement.