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Nearly 300 passengers aboard the Royal Caribbean's Oasis of the Seas cruise ship were sickened with a stomach virus since it departed Port Canaveral in Brevard County, Florida, on Sunday.

A total of 277 guests and crew members have been affected with a gastrointestinal illness, a spokesman for Royal Caribbean Cruises told NBC News on Thursday. All of the more than 8,000 guests aboard the ship will receive a refund because of the outbreak, said Owen Torres.

Those affected by the virus are being treated by the ship's medical team with over-the-counter medication, the spokesman said.

The ship, which has been on a seven-night cruise through the Caribbean, will return to Florida on Saturday, a day earlier than expected, he said.

"We think the right thing to do is to get everyone home early rather than have guests worry about their health," Torres told NBC News. "Returning on Saturday also gives us more time to completely clean and sanitize the ship before her next sailing."

Oasis of the Seas, a 1,187-foot long vessel, is one of the world's largest cruise ships, according to Royal Caribbean.