More than 300 American cruise ship passengers, including 14 who tested positive for coronavirus, were being quarantined at military bases in California and Texas on Monday after arriving from Japan on charter flights overnight.

One plane carrying cruise passengers touched down at Travis Air Force Base in Northern California just before midnight Sunday, while another arrived at Lackland Air Force Base in Texas early Monday. The passengers will remain at the bases for two weeks.

Japan's Defence Minister Taro Kono tweeted earlier that Japanese troops helped transport 340 US passengers on 14 buses from Yokohama port to Tokyo's Haneda airport. About 380 Americans were on the cruise ship.

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The United States said it arranged for the evacuation because people on the Diamond Princess were at a high risk of exposure to the new virus that's been spreading in Asia. For the departing Americans, the evacuation cuts short a 14-day quarantine that began on board the cruise ship February 5.

The State Department announced later that 14 of the evacuees received confirmation they had the virus but were allowed to board the flight because they had no symptoms. They were being kept isolated from other passengers on the flight, the US State Department and Health and Human Services said in a joint statement.

Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said Sunday that an infected person who shows minimal symptoms could still pass the virus to someone else.

It is unclear which base the 14 who tested positive for the virus went to.

Officials said the evacuees who arrived at Travis Air Force Base will be housed at a different location from the more than 200 other Americans who were already being quarantined on the base, in a hotel. Those people have been at the base since early February, when they arrived on flights from China.

No Travis airmen will have contact with the passengers, officials said.

Now that they are in the US, the cruise ship passengers must go through another 14 days of quarantine at the military facilities - meaning they will have been under quarantine for a total of nearly four weeks.

A group of ambulances from the Solano EMS Cooperative stage at the visitor centre at Travis Air Force Base, adjacent to Fairfield, California [Hector Amezucua/AP Photo]

Australia, Canada, Hong Kong and Italy were planning similar flights of passengers. Other governments, including Canada and Hong Kong, also will require the passengers to undergo a second 14-day quarantine.

Japan announced on Monday another 99 infections on the Diamond Princess, raising the ship's total number of cases to 454. Overall, Japan has 419 confirmed cases of the virus, including one death. The US has confirmed 15 cases within the country. Separately, one US citizen died in China.

Americans Cheryl and Paul Molesky, a couple from Syracuse, New York, opted to trade one coronavirus quarantine for another, leaving the cruise ship to fly back to the US. Cheryl Molesky said the rising number of patients on the ship factored into the decision.

"We are glad to be going home," Cheryl Molesky earlier told NHK TV in Japan. "It's just a little bit disappointing that we'll have to go through quarantine again, and we will probably not be as comfortable as the Diamond Princess, possibly."

She sent The Associated Press news agency a video of her and her husband boarding the plane with other Americans.

"Well, we're exhausted, but we're on the plane and that's a good feeling. Pretty miserable wearing these masks though, and everybody had to go to the bathroom on the bus," she said.

Some American passengers said they would pass up the opportunity to fly to the US because of the additional quarantine. There were also worries about being on a long flight with other passengers who might be infected or in an incubation period.

One of the Americans, Matthew Smith, said in a tweet on Sunday that he saw a passenger with no face mask talking at close quarters with another passenger. He said he and his wife scurried away.

"If there are secondary infections on board, this is why," he said. "And you wanted me to get on a bus with her?"

He said the US health officials who visited their room was apparently surprised that the couple had decided to stay, and wished them luck.

"Thanks, but we're fine," Smith said he told them.