OMAHA, Neb. — A doctor who became infected with Ebola while working in Liberia is sick but in stable condition and communicating with his caregivers at the Nebraska Medical Center, officials said Friday.

Rick Sacra, 51, is being treated at a 10-bed special isolation unit, the largest of the United States’ four. It was built to handle patients with highly infectious and deadly diseases, according to Dr. Mark Rupp, chief of the infectious diseases division at the center.

Sacra — the third American aid worker sickened with the virus — arrived at 6:38 a.m. Friday at the Omaha hospital. Sacra was wheeled on a gurney off the plane at Offutt Air Force Base, transferred to an ambulance and then wheeled into the hospital, said Rosanna Morris, chief nursing officer for the medical center.

Sacra was conscious Friday and was able to communicate with medical staff, Morris said.

The first two American aid workers infected by Ebola — Kent Brantly and Nancy Writebol — have recovered since being flown to Emory University Hospital in Atlanta for treatment. Sacra came to Omaha instead of Atlanta because federal officials asked the medical center to treat him in order to prepare other isolation units to take more Ebola patients if needed.