A health ministry official confirmed that they had been previously hospitalized in serious condition and had existing chronic diseases. The official spoke anonymously, citing office protocol.
Johns Hopkins Center for Systems Science and Engineering, which has built a map of coronavirus data including cases, fatalities and recoveries, also cites two deaths from the Diamond Princess, which brings the total death toll from the virus in Japan to three.
Per the data, 621 cases of the virus had been identified among the 3,711 quarantined passengers and crew, making the ship the site of the most infections outside of China; one Diamond Princess passenger has recovered.
The two passengers were taken to the hospital on Feb. 11 and 12, respectively, and each tested positive the day after they were admitted, Health Ministry official Masami Sakoi said. They are believed to have been infected before the ship was officially placed under quarantine on Feb. 5.
It was not immediately known why they were not tested earlier when they developed initial symptoms and consulted with the ship’s clinic, said Sakoi.
The Japanese Health Ministry also revealed Thursday that two more government officials became infected while lending clerical support to the quarantine effort on the Diamond Princess.
Four others associated with the quarantine – an official, a paramedic who carried an infected passenger, a Health Ministry worker and an emergency relief medical expert – have also been sickened.
The two deaths were the first on record of any of the people who tested positive on board. Those on board who tested positive over the course of the quarantine were taken off the ship and brought to hospitals for further evaluation and treatment.
Their deaths bring the Japanese count to three.
The Diamond Princess quarantine was ending
Passengers began to return to land Wednesday after a two-week quarantine due to coronavirus on the Diamond Princess ship, which remains docked in Yokohama, Japan.
Approximately 600 guests disembarked on Wednesday and another several hundred guests were expected to be cleared to disembark on Thursday, according to a statement from Princess Cruises shared by Negin Kamali, director of public relations.
Matt Smith, a passenger who has kept in touch with USA TODAY throughout the quarantine, was on solid ground around 1:20 p.m. local time Thursday. He and his wife, Katherine Codekas, had not yet heard of any passenger fatalities as a result of coronavirus.
The couple received their negative test results the night before on a form slipped into their state room, according to a tweet from Smith.
Although the ship's quarantine period was scheduled to end Wednesday, more than 100 American passengers on board will have to wait another two weeks to return home.
While 328 Americans had already evacuated the ship and are in quarantine in the U.S. – including 14 who tested positive for the virus – some Americans on board, including Smith, chose to finish their quarantine on the ship.