CHARLOTTE, North Carolina (AP) — Three missionaries who worked with patients infected with the Ebola virus in Liberia are back in the United States and feeling upbeat after their trans-Atlantic charter flight, the head of the North Carolina mission hosting them said Monday.

"They were amazingly vibrant this morning when I was with them," Bruce Johnson, president of the SIM USA mission, said at a news conference.

Although the three were examined upon their arrival in North Carolina and determined to be healthy, they are being held in quarantine at least three weeks dating from the time the missionaries were last exposed to people infected with the virus. That means they won't all be released at once.

For now, their quarters will be five motor homes anchored in the mission's recreational vehicle park on its wooded campus not far from the South Carolina line. Eight others, including six children, are also living on the property voluntarily until they are cleared. The eight are not under quarantine.

Johnson said there was a short list of people who have access to the area where the missionaries are staying.

The people in quarantine are having meals prepared on the SIM campus brought to them. They can sit at tables, but there is separation between them, another precautionary measure. There will be movies and games as well.

"What they can't do is hug," Johnson said.

Among the missionaries who returned is David Writebol, whose wife, Nancy, remains in isolation in an Atlanta hospital after she was returned to the United States for treatment last week. He said Writebol looked to be in good shape.

The Writebols had been in Liberia since last August, sent there by SIM USA and sponsored by their home congregation at Calvary Church in North Carolina. At the clinic, Nancy Writebol's duties included disinfecting staff entering or leaving the Ebola treatment area.

Dr. Megan Davies, the state epidemiologist with the North Carolina Division of Public Health, said the missionaries will check in twice a day, updating health officials with such information as their temperature, or if they have headaches or abdominal pains.

Such quarantines are not unusual, Davies said.

The virus is spread by direct contact with blood or bodily fluids from a sick person. Ebola can't be spread like flu through casual contact or breathing the same air as someone who is infected.