Almost 100 people were stricken with vomiting and diarrhea while on a five-day voyage around northern Europe, a major cruise operator said after the ship returned to port Thursday.
It was the third outbreak of gastrointestinal illness in three months aboard the Vision of the Seas, operated by Royal Caribbean International.
On March 4, the ship was briefly placed under quarantine after hundreds of passengers came down with gastroenteritis in a cruise off Brazil. During a separate cruise off Brazil eight days later, almost 50 passengers aboard the same boat again reported symptoms of gastroenteritis, including vomiting and diarrhea.
Brazilian health authorities pinned the blame for those outbreaks on norovirus, which inflames the gastrointestinal tract but is not life threatening. Norovirus spreads quickly in close quarters, and the virus is known for afflicting schools and cruise ships.
Royal Caribbean spokeswoman Ellen Stebekk said "it's hard to say" what caused the most recent outbreak, which appears similar in character to the Brazilian incidents.
"But this is definitely an isolated case. It's not related to those in Brazil," she said. She said the ship was thoroughly cleaned after the outbreaks in Brazil and that this was the first case of illness on board the ship since then.
Passengers began complaining of vomiting and diarrhea two days into the trip, with 94 of the ship's 2,000 passengers reporting their symptoms to the medical officer on board, Stebekk said. Two crew members also reported similar symptoms.
Symptoms were mild and lasted at most 24 hours, Stebekk said, adding that passengers were allowed to disembark freely, without being subject to quarantine, upon the ship's arrival Thursday.
The cruise began over the weekend in Oslo and traveled to Amsterdam and Bruges, Belgium, before returning to the Norwegian capital. Stebekk said the ship would leave on its next scheduled cruise Thursday afternoon.
"The Norwegian health authorities have been on board to investigate and the ship will sail this afternoon as planned after a complete clean" to disinfect the vessel, Stebekk said.