Cruise passengers must be evacuated as soon as their ship is hit by coronavirus rather than quarantined on board and risking the contagion seen on the Diamond Princess off Japan, a study has found.

Researchers claim earlier evacuation of the ship could have prevented many infections. The study comes as passengers and crew on its sister ship the Grand Princess - including more than 140 Britons - wait off California to find out if they are to be quarantined at a US port while each one is tested. The findings are likely to put pressure on the US authorities as they decide whether to evacuate or maintain a quarantine on board.

Last month more than 600 people on the Diamond Princess became infected. But researchers from the London School of Hygiene & Tropical Medicine (LSHTM) estimate that an immediate evacuation would have meant only 76 people infected.

There was criticism of the quarantine measures, with some experts saying not enough was done to isolate passengers and set up sterile zones.

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Researchers said the quarantine measures taken - such as confining passengers to their rooms - had some impact, estimating that if none had been in place 2920 people would have been infected.

Prof Annelise Wilder-Smith, from LSHTM, said: "Evacuation must happen quickly, and full quarantine is essential - people in lockdown must not mingle. In Europe we need a change in mindset, and to potentially implement more draconian measures. We need a community response.

"The Diamond Princess reported an outbreak of covid-19 on Feb 3 as it lay off the Japanese coast. Initially 10 people were infected, but by Feb 20, 619 passengers were sick. The decision was made to evacuate and more than 3000 passengers left. By Feb 24, two passengers had died. The following day, the Japanese health ministry ordered a 14-day on-board quarantine and rushed to close its ports to all other cruise ships.

Professor Wilder-Smith, who led the study, added: "What's important is to learn to ensure future effective control measures are as strong as possible." All 3500 passengers and crew on board the Grand Princess are to be tested for the virus, after initial tests found 21 infected - 19 of them crew.

US President Donald Trump has said he would prefer the passengers to stay on board, but added that he would listen to experts.

The Grand Princess was banned by California from docking after a 71-year-old man, who had been on a previous voyage, died from covid-19 after returning home. The death of a second person with links to the ship is now being investigated.

British passengers on board the Grand Princess have told of their ordeal waiting to discover their fate.

There was dismay among some that they heard the results of the tests from Mike Pence, the vice-president, on the TV news rather than directly from the ship's British captain.

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Meanwhile, a British couple with coronavirus on the Diamond Princess remain unable to return home after their latest test came back positive.

David and Sally Abel both need three negative test results to leave hospital and Mr Abel's final test showed infection.

-The Sunday Telegraph