The ambulance carrying Dr. Rick Sacra, 51, who was infected with Ebola while serving as an obstetrician in Liberia, arrives under police escort at the Nebraska Medical Center in Omaha on Friday. Sacra, who served with North Carolina-based charity SIM, is the third American aid worker infected by the Ebola virus. He will begin treatment in the hospital's 10-bed special isolation unit, the largest of four such units in the U.S.
