Updated at 8:09 p.m. ET

There are 65 new coronavirus cases aboard the Diamond Princess cruise ship, which has been under a quarantine since last week, Japan's health ministry announced Monday. With the latest cases, a total of 135 people from the ship have been confirmed to have the respiratory virus.

Those newly diagnosed include 45 Japanese and 11 Americans, as well as smaller numbers of people from Australia, Canada, England, the Philippines and Ukraine, according to Princess Cruises.

Even before the latest cases were confirmed, the cruise ship already represented the largest cluster of Wuhan coronavirus cases outside mainland China. The virus, identified as 2019-nCoV, has killed more than 1,000 people in China, where more than 42,000 people have been infected since it emerged in the city of Wuhan, in Hubei province.

The Diamond Princess is under a 14-day quarantine that's set to expire on Feb. 19. But health officials say the quarantine period could be extended for any passengers and crew members in close contact with people newly diagnosed with the strain of coronavirus.

"They need to remain in quarantine for 14 days from last contact with a confirmed case," the World Health Organization said on Sunday, referring to anyone who had been in close contact with someone infected.

As officials revealed the new test results, they did not specify how many close contacts those patients might have had on the ship.

"The captain made an announcement that the Japanese authorities were concerned about the new cases," passenger Young Wo-sang of Hong Kong told the South China Morning Post. Young added, "But he stopped short of saying whether we can leave on Feb. 19. So we just don't know when we are going to leave."

Many cases of coronavirus are mild, with symptoms ranging from a fever and cough to a flu-like condition. But patients can develop severe pneumonia, and about 2% of Wuhan coronavirus cases have been fatal, the WHO says.

Passengers aboard the Diamond Princess have been told to stay in their rooms for all but brief periods of the day, with the crew bringing meals and other necessities to their doors.

The cruise ship had roughly 3,700 passengers and crew members aboard when it arrived at the Yokohama terminal south of Tokyo early last week. Japan's health ministry has been taking people infected with the coronavirus off the cruise ship using special sanitation measures, such as a tentlike tunnel and white medical suits. Patients are then transported to local hospitals with infectious-disease wards.

The U.S. Embassy in Tokyo says that it has been visiting the Americans who have been hospitalized and that it has helped passengers aboard the ship get medications. Joe Young, the U.S. chargé d'affaires in Tokyo, says the embassy is also sending a daily email to all Americans aboard the ship.

Matthew Smith — who has been documenting his shipboard meals and bemoaning the lack of sufficient coffee on Twitter — said a recent embassy email told passengers that "the safest option to minimize the risk of infection is to remain in your cabin on the ship."

To limit the potential spread of the coronavirus, passengers are allowed to visit the deck only in shifts, for roughly 90-minute periods. They're also checking their temperatures regularly, using thermometers distributed by the crew. During their brief time in larger groups, the passengers are asked to keep their distance from other people and to wash their hands thoroughly afterward.

Princess Cruises has announced compensation for the passengers — some of whom are facing four weeks on the ship because of the quarantine — saying it will refund their full fare and other expenses, from air travel to hotel and transportation costs.

"In addition, guests will not be charged for any onboard incidental charges during the additional time onboard," the company said.

The cruise line said it will also give guests a future travel credit for a trip equal to the fare they paid for the current voyage — which officially ended Feb. 4, when the ship was held at the Japanese port.

To ease the strain of prolonged isolation, Princess Cruises announced last week that it is providing free Internet and phone service to passengers. And to stave off boredom, it also expanded the passengers' TV and movie options, along with offering games, puzzles and other distractions.

Another cruise ship, Holland America's MS Westerdam, is now on its way to Thailand after spending several days with nowhere to go when Japan — its final destination — denied entry to several of its ports, including Yokohama. Officials in Taiwan, the Philippines and Guam also had denied entry.

Holland America called the predicament "a very dynamic situation."

The ship, which has more than 2,200 people aboard, left Hong Kong for a 14-day cruise on Feb. 1.

"The ship is not in quarantine and we have no reason to believe there are any cases of coronavirus on board despite media reports," Holland America said.

The company says the Westerdam will now end its ill-fated cruise by disembarking passengers in Bangkok on Feb. 13. According to , the ship was off Vietnam's southern coast on Monday.

"All guests will be disembarking in Bangkok for their forward flights home," Holland America said. It added that the passengers will get a full refund for the trip, along with a credit for a future trip.

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