Cruise Ship Travel and the Spread of COVID-19 – Australia as a Case Study

Introduction: cruise ship linked covid-19 outbreaks have been identified as a potential source of community transmission of covid-19 in australia and worldwide. the risk factors and potential mitigation around covid-19 infections on cruise ships and communities is a research gap. methods: a correlation and regression analyses for risk factors for covid-19 attack rates oncruise ships worldwide with reported covid-19 from january 1, 2020 to may 11, 2020 were performed, with a more detailed analysis done for australia. geospatial emerging hot spot analysis during key time periods was used to assess temporal trends in spatial clustering of covid-19 cases related to two cruise ship events in nsw, australia. results: for 36 cruise ships with global covid-19 cases, available cabins had a moderate inverse correlation with the attack rate (-0.4154; 95% ci [-0.0002, -0.00003], p < 0.0118). the number of cabins, the number of decks with cabins, and passenger-to-space ratio were significantly associated with attack rate, however, the duration at sea was not. by may 2020, cruise ship passengers made up 14.9% of covid-19 cases in australia and 27% of the covid-19 related deaths. emerging hot spots of community transmission in sydney occurred during 1-2 incubation periods of two cruise ship events. conclusion: mitigation of risk on cruise ships should focus on spatial design and reducing crowding, including rapid surveillance and on-board testing. to mitigate this risk during the era of covid-19, all passengers disembarking an infected ship should be quarantined for at least the 14-day window period and tested for covid-19, regardless of symptoms. vaccination should be a pre-requisite for travel of any kind once available.