[1][2] The Diamond Princess departed from the Port of Yokohama on 20 January 2020 for a round-trip billed as a tour of Southeast Asia during the Lunar New Year period,[3][4] with 2,666 passengers and 1,045 crew on board.

On 31 January, the ship docked in Taiwan, which according to Vice Premier Chen Chi-mai was "the earliest country to activate epidemic prevention measures against this disease.

"[6] A paper in the Journal of Medical Internet Research authored by Chen, describes how the passengers of the COVID-19 stricken cruise ship were later traced using mobile phone geolocation, and how their 627,386 contacts were alerted through text messaging.

[9] Over the next few days, the cruise ship had shows and dance parties as usual and also continued to open public facilities that attract large crowds, including fitness clubs, theatres, casinos, bars, and buffet-style restaurants.

[9] On the evening of 3 February, the cruise ship returned to Yokohama Port and anchored off the coast of Daikoku Pier without docking.

[9] On 5 February, the authorities announced positive test results for SARS-CoV-2 for 10 people on board, the cancellation of the cruise, and that the ship was entering quarantine for 14 days based on World Health Organization guidelines.

[11][12][13][14][15] A total of 3,700 passengers and crew were quarantined by the Japanese Ministry of Health, Labour and Welfare for what was expected to be a 14-day period, off Yokohama.

[20] The numbers overwhelmed local medical facilities, and stricken passengers were divided into three groups according to condition, and evacuated to suitable locations, allowing intensive care to perform as intended.

[28] On the morning of 17 February (Japan time), two U.S. government-chartered planes departed for the United States, carrying hundreds of U.S. citizens who were passengers of the cruise ship.

Among about 400 American passengers, 328 boarded the planes, excluding those who expressed their intention to stay on the ship and 44 under treatment in Japan.

[35] On 18 February, Kentaro Iwata, an infectious disease expert at Kobe University, uploaded a video on YouTube in which he raised questions about the measures taken to prevent epidemics on the "Diamond Princess" shortly after boarding the ship.

[9][39] In early March 2020, Indonesia evacuated 69 Indonesian crew of Diamond Princess, after their COVID-19 test results in Japan were negative.

The 68 people with negative tests disembarked at Sebaru Island for observation and the one positive case was evacuated by helicopter to Persahabatan Hospital.

[46] Kentaro Iwata, an infectious diseases expert at Kobe University who visited the ship, strongly criticised the management of the situation in two widely circulated YouTube videos published on 18 February.

[52] Japanese officials denied the accusations and argued that the zoning on board, of course, was not perfect, but it was not insane from the medical point of view.

[53][54][52][55] Yoshihiro Yamahata and Ayako Shibata, two medical doctors who attended to the passengers as first responders, wrote later that "At the beginning of implementation of the quarantine, we had to enact measures based on limited information, which is confusing" and that "it was thought that COVID-19 could not be spread via human-to-human transmission.

[58][59][60] Takayama also revealed that Iwata was forced to leave the ship in two hours and only looked around the lounge, and he had been dismissed due to trouble with DMAT members and staff.

[60][54] A preliminary report based on the first 184 cases by Japan's National Institute of Infectious Diseases (NIID) estimated that most of the transmission on the ship had occurred before the quarantine.

[62][63] Dr. Norio Ohmagari, top government adviser and director of Japan's Disease Control and Prevention Center admitted that the quarantine process might not have been perfect.

[68] Professor Hiroshi Nishiura of Hokkaido University, a member of Novel Coronavirus Expert Meeting, analyzed the days when they were infected based on the data of the onset date and incubation period of passengers and crews.

However, the crew, who continued to support the lives of passengers as "essential workers", became infected a week after the cruise ship anchored.

[70] Those infected got CT scans even asymptomatic and mild symptoms at the SDF Central Hospital, and half of them were found to be abnormalities.

Captain Tamura, a medical officer at The SDF Central Hospital, believes that the progression of inflammation in the patient's lungs in the absence of subjective symptoms is one of the reasons why the infections, which were thought to be mild, seemed to worsen rapidly.

It was found that the deterioration of the patient's condition can be sensed by detecting decreased SpO2 (blood oxygen saturation) in the elderly and tachypnea in the young.

However, there were several cases in which PCR tests showed that they were negative despite having close contact with infected patients who got CT scans and had "frosted glass-like shadows" in their lungs.

The findings indicate that the 11083G > T mutation of SARS-CoV-2 spread during shipboard quarantine and arose through de novo RNA recombination under positive selection pressure.

[1] Between February and April 2020, Japanese government officials declared 13 fatalities from the ship, while one other person was evacuated from the vessel and died in Australia.

[83] Canadian documentarian Mike Downie's film The COVID Cruise, about the Diamond Princess outbreak, aired in November 2020 as an episode of CBC Television's science documentary series The Nature of Things.

[122] American novelist and writer Gay Courter wrote a book in 2020, chronicling her experience aboard the ship during the crisis.