Royal Caribbean Group has announced that 48 people on its Symphony of the Seas cruise ship tested positive for COVID-19 on Monday.
This fuels concerns that the new omicron variant of coronavirus could put a damper on a recovery in the cruise industry.
The cruise operator said it had 6,091 guests and crew members on board the ship, which ended a week-long cruise in Miami on Saturday after setting sail on 11 December.
The passengers who tested positive were asymptomatic or mildly symptomatic, Royal Caribbean said in a statement, adding that six guests were disembarked earlier in the cruise and transported home.
95 per cent of the community on board were fully vaccinated, while 98 per cent of those who tested positive were also fully vaccinated, according to the cruise line.
The Symphony ship's future itineraries will not not impacted, it added.