A COVID-19 outbreak on a Carnival Cruise Line ship that sailed from Galveston, Texas, to Belize is one of the largest reported on a vessel sailing from the United States since cruises relaunched this summer.

The 27 cases on the Carnival Vista reported by the Belize Tourism Board include 26 crew and one guest. All are vaccinated and have either mild or no symptoms, The Washington Post reported. The ship, which has 2,895 passengers -- 96.5 percent of whom are vaccinated -- and 1,441 crew, 99.9 percent of whom are vaccinated, continued its voyage and arrived in Cozumel on Thursday.

The crew members "remain in quarantine and/or isolation on board," Carnival spokesman Chris Chiames said, The Post reported. He added the company disclosed last week that there were positive cases and that the ship's passengers have received a series of updates about the outbreak.

New mask rules for some indoor locations were implemented on all Carnival ships last weekend. That policy took effect early, on the night of Aug. 4, on the Carnival Vista, The Post reported. Effective this Saturday, Carnival will also require all passengers -- regardless of their vaccination status -- to show proof of a negative coronavirus test taken within three days of boarding.