OMAHA, Neb. >> A doctor who became infected with Ebola while working in Liberia — the third American aid worker sickened with the virus — is sick but in stable condition and communicating with his caregivers at the Nebraska Medical Center.

Dr. Rick Sacra, 51, is being treated at a 10-bed special isolation unit, the largest of the United States’ four, officials said Friday. 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 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 — Dr. 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.

Sacra, a doctor from Worcester, Massachusetts, who spent 15 years working at the Liberia hospital where he fell ill, said he felt compelled to return after hearing that two other missionaries with the North Carolina-based charity SIM with whom he’d worked were sick. He delivered babies at the hospital, and was not involved in the treatment of Ebola patients, so it’s unclear how he became infected with the virus.

An estimated 2,100 people have died during the outbreak, but Ebola has not been confirmed as the cause for all of the deaths.

Dr. Phil Smith, medical director of the Omaha unit, has said a team of 35 doctors, nurses and other medical staffers will provide Sacra with basic care, including ensuring he is hydrated and keeping his vital signs stable.

The team is discussing experimental treatments, including using blood serum from a patient who has recovered from Ebola, Smith said. There are no licensed drugs or vaccines for the disease, but about half a dozen are in development.

Rupp said he’s unaware whether Brantly and Writebol have been asked about donating blood serum for Sacra.

“These folks are friendly and know one another, and they would presumably be willing to help their compatriots,” Rupp said, adding a battery of tests must first be performed, including one to ensure that any blood is compatible with Sacra’s.

Doctors with the Omaha hospital have repeatedly said Sacra’s transfer to Omaha posed no threat to the public, noting Ebola is transmitted through close contact with an infected person.

SIM president Bruce Johnson said Friday that Sacra’s wife, Debbie, is making arrangements to care for their three sons and preparing to fly to Omaha this weekend.

“Rick would actually be somewhat embarrassed by all this attention,” Johnson said, adding tearfully that Sacra apologized to SIM officials in an email after he was diagnosed earlier this week. Sacra told them he knew an evacuation would be difficult.

“So I don’t expect one,” Sacra’s email said. “Jesus is right here with me in Liberia.”