Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (XII)

Orouba Almilaji  1,2

1 Medical Science and Public Health Department, Bournemouth University, Bournemouth, UK
2 Department of Population Health Sciences, School of Population Health & Environmental Sciences, Faculty of Life Science and Medicine, King’s College London, London, UK

Received: July 31, 2020
Revised: December 22, 2020
Accepted: December 27, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.200495  

Cite this article:

Almilaji, O. (2021). Air Recirculation Role in the Spread of COVID-19 Onboard the Diamond Princess Cruise Ship during a Quarantine Period. Aerosol Air Qual. Res. 21, 200495. https://doi.org/10.4209/aaqr.200495


  • Infection rate in cabins with previous case was not statistically different than those without.
  • Age of subject was found not to be a confounding factor.
  • Conflicting results from previous studies of this outbreak are largely explainable.
  • Airborne transmission through the HVAC system could explain the virus spread on the ship.
  • Recirculated air and inadequate air filtration likely increased airborne transmission.


The Diamond Princess cruise ship is a unique COVID-19 transmission case because of the high testing capacity and the confined environment. This exploratory study aims to raise the hypothesis regarding the role of poor ventilation systems in the spread of COVID-19 by analysing count data collected by the onboard clinic during the outbreak, and considering the deck plan and design of the air conditioning system of the ship. Observed symptomatic infection rate after day 5 (incubation period median day) of the quarantine, in cabins without previous confirmed cases are compared to that in cabins with previous confirmed cases. Accordingly, the observed symptomatic infection rate in cabins without a previously confirmed case (1.2%) was higher than for cabins with a previously confirmed case (0.8%); however, the difference was not statistically significant. In addition, age did not appear to be a confounding variable. Airborne transmission of COVID-19 through the ventilation system onboard could explain the higher than expected virus spread into cabins without previously confirmed cases during the quarantine period; thus, this study provides further potential evidence of coronavirus transmission by aerosols. Conflicting results from other studies involving the Diamond Princess outbreak are also discussed in light of our results.

Keywords: Confined spaces, Ventilation, Airborne transmission, Filters, HVAC system

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