Analysis of the on-ship transmission of the COVID-19 mass outbreak on the Republic of Korea Navy amphibious warfare ship

OBJECTIVES: This investigation was conducted to determine the size and pattern, source, and transmission route of the coronavirus disease 2019 (COVID-19) outbreak on the Republic of Korea Navy (ROKN) amphibious warfare ship. METHODS: We investigated the characteristics of all crew members and tracked the medical records of the confirmed cases. Fourteen essential ship operation personnel were interviewed. The study design was a retrospective cohort study, and the incidence rate ratio was through a statistical program. RESULTS: The COVID-19 incidence on the ROKN amphibious warfare ship was 44.7% (38/85). It was estimated that the main propagation route started from the 1st floor worker, which spread to the same floor, and then to other floors. In the case of the working area, the incidence rate of crew members below the 1st floor without ventilation was higher than those on the 2nd or higher floors with natural ventilation. CONCLUSIONS: This case is the first case of a COVID-19 outbreak on the ROKN amphibious warfare ship, and it is estimated that the incidence rate is high because of the closed and dense environment. To prevent the spread of various respiratory diseases including COVID-19, unified mitigation such as vaccination, observing personal quarantine rules, periodic ventilation, preemptive testing, and blocking transmission through prompt contact management is necessary.