Passengers on a cruise ship that has been quarantined off the US coast were only told 21 people had tested positive for coronavirus after Vice President Mike Pence announced it on TV.
Mike Pence said all 3,500 passengers and crew on board the Grand Princess , which includes more than 140 Britons, will now be tested for COVID-19 , the disease caused by coronavirus .
He said 19 crew members on the vessel, which has been held off San Francisco, were among those that had tested positive.
US President Donald Trump has said he would prefer the passengers to stay on board, but would listen to experts if their advice is for people to be taken off.
Before the test results were released, he said allowing passengers back onto US soil who might become sick later would end up increasing the number of coronavirus cases in the country.
"I don't need to have the numbers double because of one ship that wasn't our fault," he said.
He has signed a bill to provide $8.3bn (£6.4bn) to bolster the capacity to test for coronavirus and fund other measures in the US.
At least one passenger expressed anger that the captain relayed the information 20 minutes after Mr Pence's announcement.
"Why did we not know before the vice president announced it on TV?" Kari Kolstoe, a retired teacher from Grand Forks, North Dakota, said.
The 60-year-old, who has a rare form of cancer, went on the cruise ahead of more planned treatment. She is now concerned she will miss her appointment.
She told Reuters news agency: "It's still a worry that I'm going to not get back."
It is not the first cruise ship to be affected by coronavirus.
Experts have criticised Japanese bureaucrats' handling of the Diamond Princess, where ultimately about 700 people were infected and six died after it was quarantined off the coast of Japan.
There have been claims the large number of infections occurred because the situation was mismanaged.
A British man in his 70s who was on board the ship died from the virus - the first UK fatality of the global outbreak.
Mr Pence said the US government is working with California officials on a plan to bring the Grand Princess - a sister ship to the Diamond Princess - to a non-commercial port this weekend where all passengers will be tested.
He added that it is likely the crew members caught the virus on two different voyages of the ship and he expects 1,110 members of staff on the vessel to be quarantined.
Passengers on the ship have been told to stay in their cabins, and a military helicopter has been seen lowering testing kits on to the vessel via a 950-ft rope.
The ship had been due to dock in San Francisco on Wednesday but has been held at sea.
British couple Neil and Victoria Hanlon are also among those on the boat.
They told Sky News: "There is a very ill passenger on board and they are hopefully going to airlift this passenger off some time this evening."
Mr and Mrs Hanlon said they have not been tested yet and the captain is getting annoyed about the lack of information he has to pass on to passengers.
The couple were to due to disembark the ship on today and arrive back in the UK tomorrow.
Mr Hanlon, from Somerset, continued: "Spirits are still pretty high but it's still early days.
"We're a bit fed up just sitting and lying around and getting no exercise. We're waiting for an update to tell us where we're going."
It comes after seven passengers on a previous voyage of the ship became infected with the virus, including one man who died in California's first coronavirus fatality.
Some passengers from that trip to Mexico stayed aboard for the Grand Princess's current voyage, which was returning to San Francisco after visiting Hawaii.
Samples from the coronavirus tests on board the ship were analysed at a laboratory in the San Francisco Bay area.
Passenger Michele Smith said she had been told that only people who had been on the previous Mexico voyage or those showing flu-like symptoms had to isolate themselves.
"Spirits are as high as can be under these circumstances," she said.
"We are blessed to be healthy, comfortable and well-fed."
In other developments:
US considers advising against cruise holidays
The United States is said to be considering ways to discourage people from taking cruises as part of its effort to limit the spread of coronavirus.
The proposals are being discussed ahead of a meeting between the cruise industry and US Vice President Mike Pence, who is leading America's response to the coronavirus outbreak.
The US could advise Americans to temporarily avoid travelling on cruise ships or potentially impose travel restrictions related to cruises, officials told Reuters.
Shares in Royal Caribbean Cruises, Carnival and Norwegian Cruise Line Holdings have fallen around 50% since January.
Cruise ship avoids Malta to prevent 'public unrest'
A cruise ship was forced to abandon its planned stop in Malta after doctors reportedly threatened industrial action if it was allowed to dock over coronavirus fears.
The MSC Opera, which is carrying more than 2,300 passengers and crew, will no longer stop in Malta "to avoid unnecessary public unrest", its operator MSC Cruises said.
It comes after the Medical Association of Malta and the Malta Union of Midwives and Nurses insisted they would order industrial action if the ship was allowed to berth, according to Malta Today.
MSC Cruises said "this unfortunate situation was caused locally by misinformation that had circulated regarding the medical conditions of the ship".
Earlier this week, passengers and crew on the ship were told not to leave the vessel when it docked in Greece after a former passenger contracted coronavirus.
They were kept on board the MSC Opera for several hours while officials conducted a review of the ship's full medical records.
It was then allowed to leave the port city of Piraeus and sail to Corfu as planned, MSC Cruises said.
The company has insisted there are no passengers or crew members on board the ship with any flu-like symptoms.
It is now sailing to Messina in Italy, the country facing Europe's biggest coronavirus outbreak, where it is due to arrive on Sunday.
12 coronavirus cases on Nile cruise
Twelve cases of coronavirus have been recorded on board a cruise ship on the River Nile, Egypt's health ministry said.
All of the cases were asymptomatic, meaning they carry the virus but display no symptoms of illness such as fever.
The patients were diagnosed after a Taiwanese-American woman, who had been on the cruise, tested positive for COVID-19 after she returned home.
The 12 people with the virus will be transferred to an isolation facility and those who had contact with them will be placed under a 14-day quarantine, Egypt's health ministry said.
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The cruise ship was towed to an area about 12 miles away from Luxor and placed under quarantine, according to local media.
The ship had reportedly been on a two-day Nile voyage, passing tourist sites such as the Kom Ombo temple and Edfu.
Before the ship's cases, Egypt had only diagnosed three people with the virus, one of whom it said had fully recovered after receiving treatment.
COVID-19 surfaced in China late last year and has spread to over 90 countries, with more than 100,000 infections and 3,400 deaths.
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