Four Cases of Coronavirus Disease 2019 Transferred from a Cruise Ship

An outbreak of coronavirus disease 2019 (COVID-19) that began in Wuhan, China, has spread rapidly to many countries. We herein report four cases of COVID-19 confirmed in Japan among passengers of the cruise ship Diamond Princess and describe the clinical features, clinical course, and progression of chest computed tomographic images, chest radiographs, and treatment. Although these four patients had symptoms that included a fever, malaise, runny nose, and cough, one patient had no symptoms on admission. Two of the four patients needed mechanical ventilation due to respiratory deterioration. One of the patients who required mechanical ventilation was transferred to a higher-level medical institution. Except for that patient, the other three patients were able to return home under their own power. Every patient took lopinavir/ritonavir, which was considered the most effective treatment at the time. We used it after receiving approval from the ethics committee in our hospital. In this case report, we emphasize that some patients need to be carefully monitored, even if their respiratory condition is stable at the initial presentation, as their respiratory status may deteriorate rapidly within a few days after oxygen administration begins.