COVID-19 pandemic on Diamond Princess
The Diamond Princess is a British-registered luxury cruise ship that is operated by Princess Cruises, a holiday company based in the United States and Bermuda. In February 2020, during a cruise of the Western Pacific, cases of COVID-19 were detected on board. The vessel was quarantined off Japan for two weeks, after which all remaining passengers and crew were evacuated. Of the 3,711 people on board, 712 became infected with the virus – 567 of 2,666 passengers, and 145 of 1,045 crew. Figures for total deaths vary from early to later assessments, and because of difficulties in establishing causation. As many as 14 are reported to have died from the virus, all of them older passengers – an overall mortality rate for those infected of 2%.[1][2]
COVID-19 pandemic on board Diamond Princess
Criticism[edit]
There are many criticisms of Japan's epidemic prevention measures of quarantine on cruise ships.[45]
There is the possibility that quarantine in a cruise ship is dangerous, because the cruise ship does not use HEPA filters which can effectively screen 99 percent of the particles, as is used in modern aircraft.[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.[47][48][49][50]
He called Diamond Princess a "COVID-19 mill".[51]
He said that the areas possibly contaminated by the virus were not in any way separated from virus-free areas, there were numerous lapses in infection control measures, and that there was no professional in charge of infection prevention—the bureaucrats were in charge of everything.[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.", which explains why there "might be a gap between the new and old infection control measures."[10]
While the U.S. Centers for Disease Control and Prevention commended the efforts to institute quarantine measures, their assessment was that it may have not been sufficient to prevent transmission among people on the ship.[56][57]
Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said that the quarantine process had failed.[49]
Dr. Yoshihiro Takayama, who worked on Diamond Princess as a member of the Ministry of Health, Labor and Welfare and helped Iwata get on board as a nominal member of DMAT, pointed out and corrected Iwata's errors on Facebook, saying the video could put ship passengers, crew, and medical staff in a corner.[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.[58][59]
The authorities also admitted at a press conference that Iwata, who was a member of the DMAT, tried to act alone, so they asked him to leave.[55]
The next day on 20 February, Iwata removed his videos and apologised to those involved, but still insisted the situation on the ship had been chaotic.[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.[60]
The cruise line, Princess Cruises, had first assumed there was only minimal risk and had initiated only the lowest-level protocols for outbreaks before the quarantine.[61]
By 27 February, at least 150 of the crew members had tested positive for the virus.[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.[62] A crew member reported that many of the crew had been expected to still work and interact with passengers even under the quarantine.[64][65]
Princess Cruises stated that Japan's ministry of health was the lead authority defining and executing quarantine protocols, yet Japan's ministry of foreign affairs stated that a criterion of behavior was presented but the ultimate responsibility for safe environment rested with the ship operator.[64]
Food service workers were found to have likely been the main early route of spread.[66]
46.5% of the infected passengers and crew members had no symptoms at the time of testing.[67][37][38]
The ship outbreak had a basic reproduction number of 14.8;[68] much higher than the usual 2–4.[69]
Calculations indicate that an early evacuation could have reduced the case number to just 76 cases, and that the applied quarantine reduced the case number by about 2300 cases.[68]
Survey report[edit]
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. It was speculated that passengers were infected during the three days from February 2 to 4.
However, the crew, who continued to support the lives of passengers as "essential workers", became infected a week after the cruise ship anchored.
Although strict rules were laid out and medical equipment such as N95 masks were distributed to them, it was difficult for those who were not medical workers to act as instructed.
The living environment of their communal living also increased the risk.
There was no bias or regularity in the distribution of infected sites on the cruise ship.
After searching for traces of the virus's genes, the most common place was modular bathroom floors.[9]
According to the Self-Defense Forces Central Hospital, which accepted some of the patients of the cruise ship, the average age of the patients was 68 years, and the number of men and women was about half. Cruise ship crews were mainly in their 30s and 50s, and passengers were mainly in their 70s.
48% of the patients had underlying disease. Cardiovascular diseases such as hypertension are the most common, followed by endocrine disorder such as thyroid diseases, diabetes, respiratory diseases, and cancer in that order.
The condition of patients during hospitalization was mild (41.3%) and severe (26.9%), but 31.7% had no clinical findings during the entire period.[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.
Their CT images showed a frosted glass-like shadow, a feature of the new coronavirus pneumonia.
About one-third of patients with abnormal shadows in the lungs subsequently had worsening symptoms.
They often started to get worse on the 7th to 10th day of their first symptoms, which progressed relatively slowly.
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.
They called it "Silent Pneumonia" in the sense of pneumonia that develops without any symptoms.
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.
The risk factors for mortality were mainly age (elderly people) and basic diseases, but there were a few cases in which the disease became severe even though they were neither. However, the cause was not able to be grasped.[9][70]
PCR test on board was widely carried out.
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 patients were supposed to have two PCR tests at intervals to leave the hospital, but in many cases the second was positive, even though the first was negative.
Tamura said that he felt the sensitivity of PCR test was about 70%.
The percentage of "about 70%" was also stated by the doctor at the National Center for Global Health and Medicine who treated coronavirus infections.
Sensitivity is an index to measure the proportion of positives, in the case of 70%, 30% of actual positives may be judged as false negatives and released.[70]
In fact, there were a series of people in Japan and abroad who tested positive after disembarking, even though they tested negative on board.[71][72][73][74]
Demographics[edit]
Of the 3,711 people aboard Diamond Princess on the 20 January cruise, 1,045 were crew and 2,666 were passengers.[80] The median age of the crew was 36 while the median age of the passengers was 69.[80] The passengers were 55% female and the crew was 81% male.[80] Of the 712 infections, 145 occurred in crew and 567 occurred in passengers.[81]
Legacy[edit]
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.[121]
The Last Cruise, an HBO documentary film about the Diamond Princess outbreak, was released in March 2021.[122]
American novelist and writer Gay Courter wrote a book in 2020, chronicling her experience aboard the ship during the crisis.[123]