Tokyo:Japan on Sunday confirmed that a woman who tested negative and disembarked from the coronavirus-stricken Diamond Princess cruise ship later tested positive, raising questions about the effectiveness of the quarantine measures.
Health minister Katsunobu Kato has also apologised after 23 passengers were allowed to leave without being properly tested.
The woman in her 60s returned to her home in Tochigi prefecture north of Tokyo by train after she disembarked on Wednesday, but she had a fever on Friday and tested positive on Saturday.
She was the first passenger from the ship to have tested positive in Japan after having been cleared to disembark.
The news comes as infectious disease experts and local officials have questioned the effectiveness of the quarantine period on the vessel.
"There has been a judgement that those who disembarked after testing negative had no problem, but it has now become clear that those people can turn positive," Tochigi governor Tomokazu Fukuda told a press conference late Saturday.
"We call on the government to take additional measures," he said.
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Japanese authorities have said they decided to disembark passengers who tested negative during the quarantine period as they took measures to prevent the spread of the virus -- passengers were confined to their cabins, except for brief outings on open deck when they were required to wear gloves and masks and keep their distance from fellow passengers.
However, infectious diseases specialist Kentaro Iwata has said the situation on the ship was completely chaotic and violated quarantine procedures, in blunt criticism rarely seen in Japanese officialdom.