key: cord-0710727-45vjr1ip
authors: Yamagishi, Takuya; Doi, Yohei
title: Insights on COVID-19 epidemiology from a historic cruise ship quarantine
date: 2020-08-14
journal: Clin Infect Dis
DOI: 10.1093/cid/ciaa1214
sha: dff774f3de5ce35614d7a56f1b30b5e8b2cd9d67
doc_id: 710727
cord_uid: 45vjr1ip

nan

M a n u s c r i p t 2

On January 20, 2020, the Diamond Princess left Yokoyama, Japan with more than 3,700 passengers and crew members on board and embarked upon a two-week voyage. During the cruise, a SARS-CoV-2 outbreak occurred among the passengers and crew members ultimately resulting in 712 confirmed COVID-19 cases with 13 deaths [1], which is the largest disease outbreak involving a cruise ship to date. As it docked in Yokohama on February 3 and subsequently entered ship-based quarantine, a massive public health response operation was initiated. A clinic was set up to manage and test symptomatic passengers and crew members. Transportation of critically-ill passengers to hospitals across the metro area had to be arranged promptly, and medications for quarantined passengers needed to be reconciled before personal supplies ran out. Some of the difficulties were unique to a cruise ship. Information on background health conditions was not available for all the passengers and crew members. Infection prevention and control training for crew members who continued to cater to the passengers during the quarantine proved to be a significant challenge. Furthermore, the ship needed to be moved offshore every three days to treat human waste, which interfered with multiple elements of the response operation. Despite these challenges, the event provided an unprecedented opportunity to gain insights into epidemiology and transmission The report by Plucinski and colleagues also supports probable SARS-CoV-2 transmission from asymptomatic cases. Because the analysis was conducted close to two weeks after repatriation, these asymptomatic cases can be ascertained as truly asymptomatic as opposed to pre-symptomatic. In this population, 21% (14/66) of cases were asymptomatic. Although the directionality of transmission among cabinmates was not clear since testing occurred only once in most instances, SARS-CoV-2 transmission from asymptomatic cases was strongly suggested based on the attack rate for those with asymptomatic SARS-CoV-2-positive cabinmates (63%) that was significantly higher than that for those in single-person cabins or without SARS-CoV-2-positive cabinmates (18%), and closer to that for those with symptomatic SARS-CoV-2-positive cabinmates (81%). Overall, the findings indicate that asymptomatic transmission through droplet played an important role in the outbreak, possibly in combination with environmental contamination [3] , although the risk of asymptomatic tranmission may have been higher on the cruise ship than in other circumstances because of the nature of close contacts in small cabins for prolonged periods of time. Transmission from asymptomatic cases have previously been suggested, albeit at smaller scales [4] . From the public health perspective, that transmission of SARS-CoV-2 from asymptomatic cases is almost as likely as transmission from symptomatic cases necessitates reconsideration of how Epidemiological findings on COVID-19 are increasingly linked to information from whole genome sequencing (WGS) of SARS-CoV-2. In this report by Plucinski and colleagues, the authors found that the viruses from cases in the same cabin only had 0-2 single nucleotide variants (SNVs), which supports the hypothesis of intra-cabin transmission, with transmission from a common source prior to quarantine also possible.

The use of WGS analyses is critical in uncovering hidden links and their chronology within a transmission event. As documented in this report, field epidemiology and A c c e p t e d M a n u s c r i p t 6 genomics are now fundamental components of outbreak investigation, and investment in both disciplines is needed if a country is to prepare for the next wave of emerging pathogens.

SARS-CoV-2 outbreaks have occurred on cruise ships after the Diamond Princess [7] , which underscores the likelihood that we will continue to see cruise ship infectious disease events in the future whether it is due to SARS-CoV-2 or other emerging pathogens. Guidelines from the World Health Organization [8] and the US CDC [9] are useful tools to prepare for and address cruise ship events although they do not fully address how the recommendations should be implemented. Some of the practical steps that could help cruise ships better prepare for future large-scale infectious disease events when they are allowed to sail again include requesting passengers and crew members to register their health conditions including underlying diseases and medications before embarkation, stockpiling sufficient personal protective equipment on board, and providing essential knowledge and training on infection prevention and control to crew members. The accumulating knowledge on the historic Diamond Princess outbreak brings new insights into the epidemiology of COVID-19 and should guide improved readiness towards future infectious disease events involving cruise ships.

Situation report of COVID-19 and responses of Ministry of Health, Lobour and Welfare

Haplotype networks of SARS-CoV-2 infections in the Diamond Princess cruise ship outbreak

Environmental sampling for severe acute respiratory syndrome coronavirus 2 during COVID-19 outbreak in the Diamond Princess cruise ship

Presumed Asymptomatic Carrier Transmission of COVID-19

Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study

Clinical Characteristics of Coronavirus Disease 2019 in China

Public Health Responses to COVID-19 Outbreaks on Cruise Ships -Worldwide

Operational considerations for managing COVID-19 cases/outbreak on board ships

Cruise Ship Guidance | Quarantine | CDC

Acknowledgments. The effort of YD is supported by R01AI104895, R21AI151362 and R21AI135522 from the National Institutes of Health.Potential conflicts of interest. YD have consulted for Gilead, Shionogi, Janssen,

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