Because of the illness, the ship will return to Port Canaveral, Florida, on Saturday, a day earlier than expected.
"In an abundance of caution, we have made the hard decision to return to Port Canaveral, Florida, on Saturday morning, instead of visiting Cozumel, Mexico", Royal Caribbean International states in the letter.
All of the ship's guests will get full refunds for their cruise fare paid, Torres said.
Passengers have taken to social media to report on the outbreak and reveal that they have been prevented from leaving the ship.More news: Australian actor Craig McLachlan charged with sex offences
Owen Torres, a spokesman for Royal Caribbean, which operates the vessel, said: "We think the right thing to do is get everyone home early rather than have guests worry about their health".
Passengers aboard a seven-night Royal Caribbean cruise have been struck with what can only be described as nightmarish conditions, with at least 167 of them falling ill with Norovirus. Oasis will miss the Mexico stop.
Norovirus is a contagious virus that causes vomiting and diarrhea. 100+ passengers and a crew member sick.
"During this sailing, there has been a small percentage of guests onboard who have experienced gastrointestinal illness, thought to be norovirus".More news: MCTS bus driver saves 1-year-old left alone on overpass
"In an abundance of caution, we have implemented enhanced sanitizing procedures on board.You will likely see some of these activities throughout our sailing, as we are taking all steps necessary to maintain our high health standards", Royal Caribbean wrote in a letter to guests. The report is required when 2% or more of the passengers or crew have gastrointestinal illness. Level 3 Norovirus outbreak.
Vacationers aboard the Oasis of the Seas were not allowed to disembark the cruise ship in Jamaica on Tuesday because of the outbreak on board.
Cruise ships visiting US Ports must declare to the CDC any outbreak of gastro affecting over 3 per cent of their passengers. Oasis of the Seas has passed every sanitation inspection since its first in 2010.
Norovirus has also been spreading across the United Kingdom, with a school in Hampshire having to close in December after a reported outbreak.More news: Steelers president on Antonio Brown: ‘We’ll look at all the options’
"People are still getting sick", he told ABC News. "Anything beats the cold weather in Vermont".