The CDC reports that coronavirus RNA, the genetic material of the virus that causes COVID-19, survived for 17 days on surfaces of the Diamond Princess cruise ship, after passengers had already left. The Centers for Disease Control and Prevention published the study on Monday, after examining  docked in Yokohama, Japan and the Grand Princess cruise ship docked at the Port of Oakland in California. Both ships had been quarantined prior to docking, after folks on board each ship had tested positive for COVID-19. According to the study, coronavirus RNA was found on multiple surfaces in the Diamond Princess cabins up to 17 days after passengers had vacated the ship, but before the disinfection process had commenced.

However, it was determined that transmission largely occurred between passengers prior to quarantine, and researchers could not determine if initial transmission occurred from these contaminated surfaces. As for crew members, they were mostly infected during or after quarantine. The Diamond Princess was previously reported as the site with the most cases of coronavirus outside of China. 621 people had tested positive for COVID-19, with two passengers—an 87-year-old man and an 84-year-old woman—dying from the virus. On the Grand Princess, 21 people had tested positive for coronavirus, including 19 crew members and 2 passengers. The vessel had 2,400 passengers on board.

“The results provide key information about the stability of [the virus] and suggests that people may acquire the virus through the air and after touching contaminated objects,” the National Institute of Health said in a press release. It had previously been found in a study by the New England Journal of Medicine that coronavirus can survive for 3 hours in aerosols (liquid droplets in the air, from coughs or sneezes), 4 hours on copper, 24 hours on cardboard, and 2-3 days on plastic and stainless steel. To prevent contracting coronavirus from one’s fingertips, the CDC recommends washing one’s hands for at least 20 seconds each time, and to avoid touching one’s face.