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 steepest descent method was used to solve the above nonlinear problem. An early version of this approach was combined with an approximation method to estimate the infection rate of general infection spreaders during the 2003 SARS epidemic. The method predicted the reported occurrence of all seven SARS super spreading events in Hong Kong and Singapore in 2003 (Li, et al., 2004) , in terms of both exposure times and number of infected cases. The validation of the method for Covid-19 is shown in Figure S1 . Figure 1a shows the predicted daily infection for both the 149 passengers and 48 crew. The infection probably started on Jan 28 and completed by Feb 6 for passengers ( Figure 1a ). However, crew members continued to get infected on and after Feb 6. The infection started among the passengers with a peak on Feb 3, which was the date when the ship just arrived in Yokohama. The decline of the infection after Feb 3 is expected as some passengers probably started to minimize their close contacts and social gathering. The crew infection was peaked on Feb 7, suggesting that some close contact continued to be significant among crew members after quarantine on Feb 5. This is not surprising as the crew members need to provide serves to the passengers. Kakimoto et al (2020) described the transmission among crew members during quarantine of the ship. The 3-4 day late peak infection date for the crew also suggest that infection was initiated first among the passengers, as also suggested by the study of Kakimoto et al (2020).