Four of the Americans who were exposed to a new virus on a Japanese cruise ship and were being monitored at an Omaha hospital have been released from quarantine. The University of Nebraska Medical Center says two of them never tested positive for the new coronavirus and were cleared for release Monday. Two others left quarantine on Sunday after testing negative. Eleven more people who were evacuated from the Diamond Princess two weeks ago all tested positive for COVID-19. They will have to test negative three times, 24 hours apart, before they can leave quarantine.