An Associated Press photographer

Four other American aid workers who were sickened by Ebola while volunteering in the West African outbreak have been treated at hospitals in Georgia and Nebraska. One remains hospitalized while the others have recovered. An Associated Press photographer saw a person dressed in a white protective suit get off a plane and walk to a waiting ambulance at the Frederick Municipal Airport in Maryland about 3:30 p.m. Sunday. The plane's tail number matched that of the aircraft that has been used previously to transport other Ebola patients to the United States from overseas. NIH spokesman John Burklow confirmed that the plane carrying the patient landed at Frederick. Sunday that he will seek an investigation into how a contract employee was able to sabotage a regional control center and bring Chicago's two international airports to a halt.