Transmission routes of Covid-19 virus in the Diamond Princess Cruise ship

Pengcheng Xu; Hua Qian; Te Miao; Hui-ling Yen; Hongwei Tan; Benjamin J. Cowling; Yuguo J Li

The copyright holder for this preprint (which was not peer-reviewed) is . https://doi.org/10.1101/2020.04.09.20059113 doi: medRxiv preprint predicted a peak infection 1-2 days after Feb 5, which differs slightly from our predicted peak on Feb 3. The infection among passengers was significantly reduced following the quarantine starting on Feb 5, but according to our prediction, the passenger infection was already on the way to decline from 3 Feb as they became aware of the outbreak and exercised selfdiscipline. For those infected in the staterooms with infected individual (i.e. close contact category), the infection occurred both prior to and after Feb 5 quarantine. The lack of crossroom transmission between passengers of different staterooms during the quarantine period strongly suggests that the ship central air conditioning system did not play a role, i.e. the long-range airborne route was almost totally absent in the outbreak, based on our predicted data. The Diamond Princess Cruise Ship was built and completed in 2004 by Mitsubishi Industries. A centralized full-air air conditioning system with VAV was designed and installed in all passenger staterooms and crew cabins, with 30% fresh outdoor air for staterooms, 50% for public areas and 100% for clinics and kitchen etc. A fully independent exhaust air system was installed from the bathrooms. Although no measured ventilation rate was reported for the ship, international standard such as ISO 7547:2004 requires 8 Litre/s per person, which is similar to those in offices and other public spaces (ASHRAE62.1, 2007). It was also reported that the maximum outdoor air supply was operated during the quarantine period. This probably implied that a reasonably ventilated indoor environment such as that on this ship would not result in cross transmission of the virus due to the long-range airborne route.