More than 5,000 passengers—including 428 Americans—are under a mandatory two-week quarantine after 13 passengers, including an American, on two cruise ships tested positive for coronavirus. The Diamond Princess, which has 3,700 passengers, is stranded in the sea off Japan. A previous guest who exhibited no symptoms while on the ship tested positive for the virus last weekend, which prompted Japanese health officials to test all of the passengers. The 10 people who tested positive for the virus on that ship—some of whom showed no symptoms—will be removed from the vessel and taken to local hospitals. Those who tested positive include the American, three Japanese, three from Hong Kong, two Australians, and a crew member from the Philippines, ABC News reports. The remaining passengers will be quarantined for at least 14 days and tested frequently for the virus. A second cruise ship, the World Dream, is docked in Hong Kong but none of the 1,800 people on board are allowed to get off.