Americans with underlying health conditions have been warned by the US government to avoid taking cruises amid efforts to contain coronavirus.

The edict by the US State Department came after 21 crew and passengers on board Grand Princess off the coast of California were confirmed as having tested positive for the virus.

The Princess Cruises ship had been prevented from docking since Wednesday but was granted permission to disembark passengers from today (Monday) at the port of Oakland.

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The State Department advisory came 24 hours after global cruise line body Clia warned that any action by Washington to discourage US citizens from taking cruises was “unwarranted” and at odds with the  World Health Organisation.

The State Department guidance followed US vice president Mike Pence meeting with cruise industry officials in Florida to discuss what the federal government might do.

Some executives were surprised to see the department’s warning after it emerged, according to the New York Times.

But it follows hundreds of American passengers being evacuated from Diamond Princess in Japan after the ship was quarantined due to an outbreak of coronavirus.

The State Department said in an alert on its website: “US citizens, particularly travellers with underlying health conditions, should not travel by cruise ship,”

The US Centers for Disease Control (CDC) had noted “increased risk of infection of Covid-19 in a cruise ship environment.”

The State Department added: “In order to curb the spread of Covid-19, many countries have implemented strict screening procedures that have denied port entry rights to ships and prevented passengers from disembarking.

“In some cases, local authorities have permitted disembarkation but subjected passengers to local quarantine procedures.

“While the US government has evacuated some cruise ship passengers in recent weeks, repatriation flights should not be relied upon as an option for US citizens under the potential risk of quarantine by local authorities.”

The State Department described the situation as “fluid” but noted that older adults and travellers with underlying health issues “should avoid situations that put them at increased risk for more severe disease.

“This entails avoiding crowded places, avoiding non-essential travel such as long plane trips, and especially avoiding embarking on cruise ships.

“Passengers with plans to travel by cruise ship should contact their cruise line companies directly for further information and continue to monitor the website and see the latest information from the CDC.

Clia said: “We are staying focused on the development of an aggressive, responsive plan as agreed with the meeting with vice president Pence that goes beyond the already significantly enhanced protocols in place, which we believe are a model for others.”

A Carnival Corporation spokesperson said: “While an advisory has been issued, no restrictions are in place for those who choose to take a cruise.

“Our brands have enhanced their health screening protocols, which includes thermal scans, temperature checks as well as other actions, both prior to boarding and on board our ships.

“We are currently in discussions with the CDC, World Health Organisation and other health officials, and we met as a cruise industry Saturday with US vice president Mike Pence on an aggressive industry-wide response plan.

“The health and safety of our guests and crew is our highest priority, and cruising remains one of the most attractive vacation options available.”

Foreign Office Grand Princess repatriation

Meanwhile, the Foreign Office said it was “working intensively” with US authorities to arrange a flight for an estimated 140 British nationals on Grand Princess.

A Princess Cruises spokesperson said: “Princess Cruises can confirm we have received word from state and local response operations that Grand Princess will proceed to the Port of Oakland on Monday to begin disembarking guests who require acute medical treatment and hospitalization.

“Exact timing is still being determined in a co-ordinated manner with all operations resources. These guests will be transported to medical facilities in California.

“Disembarkation will continue throughout Monday for other guests.

“Following health screenings, guests who are California residents will go to a federally operated facility within California for testing and isolation, while non-Californians will be transported by the federal government to facilities in other states. Crew will be quarantined and treated aboard the ship.

“We will provide additional information as we receive it.”