An American health care worker who experienced a high risk of exposure to the Ebola virus while in Sierra Leone was flown to a hospital in Nebraska on Sunday for observation and possible treatment, according to a hospital official.

The patient, who the official said was not showing symptoms of infection, had been expected to arrive in Omaha aboard a private air ambulance on Sunday around 2 p.m. Central time, the University of Nebraska Medical Center said in a news release on Saturday.

The patient was to be taken to the hospital’s Biocontainment Patient Care Unit for three weeks of observation, the official, Dr. Philip Smith, who is the unit’s medical director, said on Saturday.

“This patient has been exposed to the virus but is not ill and is not contagious,” Dr. Smith said. “However, we will be taking all appropriate precautions.”