Japan’s health ministry revealed the spike in cases on Monday (10 February), taking the total number of confirmed infections to 136.

Among the 66 new cases is one Briton, along with 45 Japanese, 11 US citizens, four Australians, three Filipinos, and one person each from Canada and Ukraine.

Princess confirmed last week there were 2,666 guests and 1,045 crew onboard Diamond Princess, which is being held in the port of Yokohama.

In a statement, Princess said the increase in cases was “not unexpected” and added that the quarantine end date remained 19 February.

“Princess Cruises has confirmed an additional 66 cases of coronavirus as tested by the Japanese Ministry of Health on Diamond Princess,” said the line.

“We are following guidance from the Japanese Ministry of Health on plans for disembarkation protocols to provide medical care for these new cases.

“Since it is early in the quarantine period of 14 days, it was not unexpected that additional cases would be reported involving individuals who were exposed prior to the start of the quarantine.

“The Japanese Ministry of Health has been the lead public health authority defining the testing protocols for all guests and crew on Diamond Princess. The quarantine end date remains at February 19, unless there are any unforeseen developments.

"Additional information will be shared as soon as it is made available by the Ministry of Health."

’Unprecedented situation’

In a video update, Princess Cruises president Jan Swartz said the guests and crew of Diamond Princess were the focus of Princess’s “entire global organisation”.

"In this unprecedented situation, the Japanese Ministry of Health authorities are working with us collaboratively on additional enhancements, approving new procedures as we adapt our process to the unique challenges of this situation," said Swartz.

She confirmed additional medication had been delivered to the ship and would be distributed based on medical priority, adding Princess was exploring several ways to keep guests healthy, including measures to combat any mental health issues.

Guests can access support from trained counsellors by phone in both English and Japanese, and the line has made new fitness and wellness videos available to guests.

Princess also confirmed 10 guests onboard Diamond Princess were disembarked for "non-coronavirus medical reasons" and taken to local hospitals.

It comes as concern over the spread of coronavirus worldwide continues to grow; more than 40,000 cases have been confirmed in China, resulting so far in more than 900 deaths.

On Monday, the UK government formally declared coronavirus a “serious and imminent threat” to public health, and announced new powers – including more stringent quarantine measures – to mitigate any spread of the virus in the UK.

In a statement, health secretary Matt Hancock said Arrowe Park Hospital on the Wirral and Kents Hill Park conference centre in Milton Keynes has been officially designated “isolation” facilities.