An oncologist traveling on the cruise ship at the center of a hantavirus outbreak says he's the lone American isolated at a special biocontainment unit in Nebraska . Dr. Stephen Kornfeld of Bend, Oregon , says he volunteered to help care for fellow passengers who began getting sick aboard the MV Hondius in April. He was among more than 120 passengers and crew evacuated from the ship, and flown to different countries to enter quarantine. While 15 other Americans are being monitored at the National Quarantine Unit at the University of Nebraska Medical Center in Omaha , Kornfeld was the only one taken to a separate unit after a nasal swab he took on the ship tested positive for the virus. “I feel wonderful, 100%,” Kornfeld told CNN’s “Erin Burnett OutFront” on a video call from his hospital room Tuesday. He said there was a period on the ship when he came down with flu-like symptoms including night sweats, chills and fatigue but he said he has no symptoms now.…