About 3,000 people on a cruise ship quarantined in the Japanese port of Yokohama due to the outbreak of a new coronavirus will start disembarking Wednesday as scheduled, health minister Katsunobu Kato said.

Kato told a press conference on Tuesday that test samples had been collected from all the remaining passengers of the Diamond Princess and that disembarkation is expected to be completed by Friday.

Those who tested negative will be allowed to leave without restrictions, while those who have been infected with the virus will be hospitalized. The same measures will apply to the crew.

The cruise ship was carrying around 3,700 passengers and crew from more than 50 countries and regions. The number of infections among them rose by 88 on Tuesday, bringing the total to 542.

Chief Cabinet Secretary Yoshihide Suga, meanwhile, said at a press conference that it was "appropriate" to keep the passengers and crew aboard until the two-week quarantine period ends on Wednesday.

His comments came amid questions raised by U.S. media about Japan's response to the situation aboard the Diamond Princess after a group of 328 American passengers from the ship left for home early Monday on planes chartered by the U.S. government.

Aside from those on the vessel, the number of infections confirmed in Japan rose to 61, with eight new cases reported Tuesday, including a son of an infected doctor at Saiseikai Arida Hospital in Wakayama Prefecture.

The son was the first person under the age of 20 infected in Japan, the prefectural government said, adding he has not shown any symptoms so far.

The cases also included a male inpatient at the hospital, who shared a room with another infected patient, and a male nurse in his 30s who was part of a medical team dispatched to the cruise ship, according to the local government.

In the western Japan prefecture, nine other people have already been confirmed as infected with the virus, including a man in his 50s who had not recently visited the hospital.

Two other men in their 50s and 80s confirmed to have the virus in the capital were in a serious condition, the Tokyo metropolitan government said.

A Japanese man in Aichi Prefecture and a taxi driver in Yokohama, both in their 60s, were also reported as infected, according to local authorities.

"We are seeing an increase of cases in which the route of transmission is not immediately known," Kato said. "We have to handle the situation by assuming it could spread to a certain degree."

Prime Minister Shinzo Abe instructed his ruling Liberal Democratic Party to consider postponing or reducing the size of its annual general meeting scheduled for March 8 as infections spread.

At a government task force meeting on measures to prevent the spread of the virus, Abe urged people with cold-like symptoms such as a fever to "take time off school or work and refrain from leaving the house."

Meanwhile, four Japanese nationals who were aboard the Westerdam, a cruise ship which was earlier refused entry to Japan due to suspected cases of infection, arrived at Tokyo's Haneda airport early Tuesday, Foreign Minister Toshimitsu Motegi said.

They had cleared initial screening in Cambodia where they disembarked and were undergoing further testing following their arrival in Japan, he said.

Another Japanese national working as a crew member on the Westerdam wished to remain with the vessel, Motegi said, adding the ministry would stay in touch and provide necessary help.

On Tuesday, WHO Director General Tedros Adhanom Ghebreyesus told a media briefing that the virus was fatal in about 2 percent of reported cases and appeared to be "not as deadly as other coronaviruses including SARS and MERS."

The fatality rate of MERS was over 30 percent, while that of SARS was about 10 percent, according to the WHO.

Based on data provided by China on more than 44,000 confirmed cases of infection, over 80 percent of patients develop only mild symptoms before recovering.

In around 14 percent of cases the virus causes severe symptoms, such as pneumonia and shortness of breath, and in about 5 percent patients develop critical symptoms including respiratory failure, septic shock and multiorgan failure, he said.

The WHO director general also said the risk of death increases with age and there are relatively few cases among children.

While the data appear to show a decline in new cases, he called for continued vigilance, saying, "It's too early to tell if this reported decline will continue."

The WHO's situation report dated Monday showed 71,429 people had been confirmed as infected with the virus worldwide, with those in mainland China making up 70,635 of the total cases.

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