The number of passengers on a quarantined cruise ship in Japan who have been diagnosed with the coronavirus climbed to 174 on Wednesday morning.

Thirty-nine new cases were confirmed in the past 24 hours on the Diamond Princess, which has been docked at the Port of Yokohama since Feb. 3, ABC News reported. Japan’s Ministry of Health, Labor and Welfare said a quarantine officer has also been infected.

Infected passengers have been brought to shore for treatment, while remaining passengers have been quarantined in their rooms on the ship. Some experts have questioned the efficacy of the quarantine since the virus has continued to spread onboard.

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"The issue with quarantine remains the lack of ability in a closed environment like this to maintain infection prevention measures on a ship," Dr. Eric Cioe-Pena, director of global health at Northwell Health in New Hyde Park, N.Y., told ABC. "We are seeing numbers increase dramatically, which likely means that there is ongoing spread of the virus on these ships. That’s concerning, as its creating a second epicenter of the infection, in a Japanese port."

A spokesperson for Princess Cruises told the network the quarantine was in keeping with guidance from the Japanese government.

"We are following guidance from the Japan Ministry of Health on plans for disembarkation protocols to provide medical care for these new cases," the spokesperson said in a statement Wednesday, according to ABC.