(CNN) — Despite stringent measures supposed to keep ocean cruises Covid-free, operator Royal Caribbean says at least 48 people on board one of its ships that docked in Miami at the weekend have tested positive for the virus.
The Symphony of the Seas, the world’s biggest cruise ship, was carrying more than 6,000 passengers and crew on a week-long journey around the Caribbean when a guest tested positive, prompting wider contact tracing, according to Royal Caribbean.
The Symphony of the Seas was carrying 6,091 passengers and crew members. In a statement, Royal Caribbean said that a guest tested positive during the voyage, and subsequent cases were detected following contact tracing.
It said 95% on board were fully vaccinated. Of the people who’ve since tested positive, 98% were fully vaccinated. It’s not yet known whether the highly infectious Omicron variant of coronavirus, currently spreading rapidly around the world, was responsible for the cases detected.
Crew members are also required to be fully vaccinated and test “at least once a week.”
Unvaccinated children on board Symphony of the Seas were required to show a negative PCR, and also test negative at the terminal pre-departure.
Royal Caribbean says it also implements additional health and safety measures, such as enhanced cleaning. On US-based cruises, masks are now required to be worn in indoor public areas — this policy was recently updated to extend mask-wearing requirements for fully vaccinated passengers.
“Each person quickly went into quarantine,” reads a Royal Caribbean statement on the Symphony of the Seas outbreak. “Everyone who tested positive were asymptomatic or had mild symptoms, and we continuously monitored their health.”
Symphony of the Seas departed from Miami, Florida on December 11, stopping at Caribbean ports St. Maarten and St. Thomas, as well as Royal Caribbean’s private island, called CocoCay.
The cruise line says in its statement that it disembarked six positive cases earlier in the cruise, while the other positive travelers disembarked on December 18, when the voyage came to an end.
The cruise line added that Symphony of the Seas’ future voyages weren’t impacted.
CNN’s Lechelle Benken contributed to this report.