An oncologist traveling on a cruise ship amid a hantavirus outbreak says he’s the lone American isolated at a special biocontainment unit in Nebraska. Dr. Stephen Kornfeld says he volunteered to help care for sickened passengers aboard the MV Hondius. Now he’s among 18 Americans under observation at medical facilities that specialize in treated highly infectious diseases. Kornfeld is the only passenger at the Omaha, Nebraska, medical campus after one of two tests on a nasal swab he took on the ship came back positive. Kornfeld told CNN’s “Erin Burnett OutFront” on Tuesday that he feels great and has no symptoms. He’s awaiting new test results later this week.