Japan will keep close tabs on the health conditions of people who were allowed to leave a coronavirus-hit cruise ship after testing negative for the virus, the country's health minister said Sunday, following revelations that one such person was found infected soon after returning home.

The country's health authorities will make daily phone calls to hundreds of people who have disembarked from the Diamond Princess docked in Yokohama, and have already asked them to avoid using public transportation and to wear masks when they come into contact with others, Katsunobu Kato said.

On Saturday, authorities in Tochigi Prefecture said a woman in her 60s, who left the cruise ship and returned home in the prefecture using public transport, tested positive for the pneumonia-causing virus earlier that day. Her test results came back negative on Feb. 15, four days prior to her disembarkation.

"I have to take it seriously," said Kato, in commenting on her infection, at a press conference.

The health minister said during a parliamentary session last Wednesday that he sees no need to quarantine Diamond Princess passengers who tested negative, once they disembark from the ship.

"The National Institute of Infectious Diseases suggested that people who had been under control for 14 days, tested negative and were given final approval about their health, can use public transport. And I made the final judgement (to go ahead with the policy)," the minister said at the time.

On Sunday, Prime Minister Shinzo Abe instructed his government to swiftly draw up a basic policy to curb the spread of the new coronavirus in Japan.

Speaking at a meeting, Abe called for quickly building a system to provide necessary medical services in an effort to prevent people infected with the pneumonia-causing virus from falling seriously ill.

Health, Labor and Welfare Minister Kato will lead work to craft the policy, which Abe said will involve providing information to the public and companies, as well as implementing measures to block the spread of infection and provide medical services to patients. The policy is expected to be announced Tuesday.

"Curbing the speed of an increase in the number of patients is extremely important to contain an epidemic," the prime minister said, citing rising cases of infection from unknown routes in the country.

So far, around 840 people have tested positive for the virus in Japan. Most of the cases, or 691, involved passengers and crew of the vessel.

Meanwhile, the health ministry said Sunday a Japanese man in his 80s who was on the Diamond Princess has died from pneumonia, bringing the number of deaths among people who boarded the coronavirus-hit vessel to three.

However, the ministry refrained from clarifying whether the man tested positive for the virus or whether he was a passenger or a crew member, citing a lack of consent from his family. The man had pre-existing conditions, the ministry said.

In Japan, two Japanese passengers -- an 87-year-old man and an 84-year-old woman -- died from COVID-19, the official name of the pneumonia caused by the new virus, last Thursday.

Their deaths followed the first COVID-19 death in the country, of a woman in her 80s, a week earlier. She was unrelated to the cruise ship.

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