Testing for influenza-like illnesses had been conducted on a limited number of specimens before and after the start of the outbreak. Testing of specimens obtained from 5 crew members during the week before the outbreak identified 3 crew members who were positive for human rhinovirus or enterovirus, 1 who was positive for respiratory syncytial virus (RSV), and 1 with no pathogens detected. After the outbreak was identified on March 23, specimens from 16 crew members were tested: 10 crew members had no pathogens detected, 3 were positive for human rhinovirus or enterovirus, 2 were positive for coronavirus OC43 (not SARS-CoV-2), and 1 was positive for both human rhinovirus or enterovirus and RSV.