Haplotype networks of SARS-CoV-2 infections in the Diamond Princess cruise ship outbreak

On February 5, 2020, the Diamond Princess cruise ship was put under quarantine offshore Yokohama, Japan, after a passenger who disembarked in Hong Kong was confirmed to have coronavirus disease 2019. Whole-genome sequencing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and a network/phylogeny analysis of the outbreak suggested that there was a single introduction of SARS-CoV-2, which disseminated among passengers on the ship through possible mass-gathering events in the recreational areas. These findings provide information useful for preventing future outbreaks on cruise ships and emphasize the importance of genome-based network/phylogeny analysis to elucidate possible transmission routes in outbreak situations.