How many people have tested positive for the coronavirus on board?

Japan has confirmed 247 cases overall since the virus was first detected in the Chinese city of Wuhan in late December.

What has it been like for passengers on board?

Those who have tested positive have been evacuated to onshore medical facilities. Health officials announced on Thursday that they intended to move elderly people and those with pre-existing conditions off the ship in the coming days even if they tested negative.

Many of those on board have described the tedium of being confined to their cabins and anxiety about the virus spreading further, or expressed frustration at the lack of timely information about the outbreak coming from Japanese authorities.

“It’s getting tougher by the day, and certainly for passengers with the inside cabins, it’s not easy,” said British passenger David Abel in a Facebook live-stream on Thursday.

Some passengers have praised the efforts of the crew to keep up people’s spirits, including putting together videos featuring magic tricks and dance and stretching routines.

Matthew Smith, a passenger from the United States, has racked up thousands of followers on Twitter with his regular upbeat appraisals of the ship’s food.

“Don’t believe the honeymooners who would rather be in an American hospital,” he wrote in one post last week. “You might have to drag me off the ship when the quarantine ends.”

Why has Japan’s handling of the outbreak been so controversial?

Some medical experts have questioned the wisdom of placing the passengers and crew in quarantine in the close confines of a ship, rather than removing them to dedicated facilities on the shore.

“Ideally, the crew members and the passengers should be quarantined at holiday camps,” said David Shu-Cheong Hui, the director of the Stanley Ho Centre for Emerging Infections Diseases in Hong Kong. “The event on the Diamond Princess cruise would fit the description of a super spreading event.”

Kumar Visvanathan, an infectious diseases expert at the University of Melbourne, said a cruise liner such as the Diamond Princess would be ill-equipped to prevent the spread of infections.

“It seems that though isolation in individual cabins is somewhat effective, the increasing numbers of symptomatic infections seems to suggest active infections even with the best precautions are occurring,” Visvanathan said.

“It is clear that cruise ships and their individual cabins are not made for isolation purposes and depend heavily on individual participation in the isolation procedures, including respiratory hygiene, cough etiquette and hand hygiene,” he said.

Visvanathan said, however, that gauging the correct response was difficult as authorities had to consider the welfare of both the general public and those on the ship.

“I think the way to look at it is there are two disparate concerns that need to be balanced,” he said. “The first is the protection of the outside community which I think the Japanese government is taking as most important, and in this case isolation on board is the most efficient way to prevent infection of the Japanese population.”

Criticism has also been levelled at authorities for not testing all of those on board from the start. After initially insisting that they did not have the resources to test everyone on board, health officials said on Thursday that they were now aiming to test 1,000 people a day.

The World Health Organisation, however, has defended Japan’s handling of the situation, saying the country was ensuring those who were ill received proper treatment, the most important consideration during such an outbreak.