Transmission of the novel coronavirus onboard the Diamond Princess

COVID-19: Transmission of the novel coronavirus onboard the Diamond Princess. Spencer EA, Heneghan C.

Published on June 22, 2020

Reference Mizumoto K, Chowell G. Transmission potential of the novel coronavirus (COVID-19) onboard the diamond Princess Cruises Ship, 2020. Infect Dis Model. 2020;5:264‐270. Published 2020 Feb 29. 2020
Study type
Country Japan
Setting The Diamond Princess cruise ship
Funding Details Japan Society for the Promotion of Science (JSPS) and the joint NSF-NIH-USDA Ecology and Evolution of Infectious Diseases program.
Transmission mode Close contact, person to person
Exposures Cruise Ship

Bottom Line

Passengers and crew in the cruise ship experienced high transmission rates, hypothesised to be due to the close quarters and confined living spaces.

Evidence Summary

454 confirmed cases on board. Among the 3,711 passengers and crew on board, there were 621 (17%) symptomatic and asymptomatic people with positive COVID-19 tests. 

20th Jan
  • Departed from the Port of Yokohama
  • Index case embarked
25th Jan
  • Arrived at the Port of Hong Kong
  • Index case disembarked in Hong Kong
  • Departed from the Port of Hong Kong
27th Jan
  • Arrived at the Port of Chan May (Vietnam)
  • Departed from the Port of Chan May (Vietnam)
28th Jan
  • Arrived at the Port of Cai Lan (Vietnam)
  • Departed from the Port of Cai Lan (Vietnam)
31st Jan
  • Arrived at the Port of Keelung (Taiwan)
  • Departed from the Port of Keelung (Taiwan)
1st Feb
  • Arrived at the Port of Naha (Japan)
  • Departed from the Port of Naha (Japan)
  • The index case was confirmed
4th Feb
  • Arrived at the Port of Yokohama (Japan)
  • Passengers and crews were asked to stay on the ship for quarantine
  • Health status of all passengers and crew members were checked by questionnaire by quarantine officers
5th Feb 
  • A lab-confirmed case of COVID-19 was detected.
  • Quarantine for 14 days begins at 7 am.
  • Passengers requested to stay in their cabins.
18th Feb
  • End of quarantine

What did they do?

This study looked at transmission during the outbreak of COVID-19 on the Diamond Princess cruise ship, January to February 2020. 

PCR laboratory tests were used to test for COVID-19 among the passengers and crew of the ship, prioritising symptomatic or high-risk groups.

The study used mathematical modelling and time-series incidence data describing the trajectory of the outbreak among passengers and crew members, to characterize how the transmission potential varied over the course of the outbreak.

Study reliability

The dataset was incomplete due to missing the date of onset for around a third of cases. 

This is an unusually confined setting for a large number of people and may not represent a typical transmission setting. A total of 103 laboratory-confirmed symptomatic cases with unknown onset dates were not in the analysis.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No Unclear Yes No

About the authors

Carl Heneghan

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.

Tom Jefferson

Tom Jefferson

Tom Jefferson, epidemiologist.