Abstract
The event of the Diamond Princess, with a total of 712 (as of 17 March 2020) persons infected on the cruise ship, attracted global attention as the largest disease cluster outside China for the period 7 to 24 February 2020. Representing the Ministry of Health, Labour and Welfare, the authors were heavily engaged in the quarantine operation on the cruise ship ourselves. During the quarantine period from 5 to 23 February 2020, when the last group of the quarantined passengers left the ship, a series of measures have been conducted under the principles of i) zero deaths among all on board, ii) rapid establishment and thorough implementation of an infection control system, and iii) maintenance of health conditions and relief of anxieties among passengers and crew members. The case of Diamond Princess has implications of more than a cruise ship but deserves full scientific analysis to learn lessons from this operation as well as to study the characteristics, particularly the transmission of COVID-19.