An outbreak of Clostridium perfringens infection on a training ship anchored in Busan, Korea

In September 2023, an outbreak of food-borne disease occurred among students on a training ship docked in Busan. This was an epidemiological investigation with the aim of improving infection prevention activities and group meal service practices on board ships. In this study, a case was defined as an individual who experienced diarrhea more than twice a day during their training period aboard the training ship. A total of 171 exposed individuals including 6 food handlers was well-defined; therefore, a retrospective cohort study was conducted. We administered a questionnaire and conducted laboratory tests including 38 rectal swab samples. Relative risk (95% confidence interval) for each food item was calculated. Of the 165 students and school staff members, 41 met the case definition, resulting in an attack rate of 24.8%; all cases were students. The shape of the epidemic curve was unimodal, with the peak from 0:00 to 06:00 on September 7, 2023. Clostridium perfringens was detected in 9 cases, and no other pathogens were found. Significant relative risk was shown in 11 different food items. Clostridium perfringens was the causative pathogen of this outbreak on the training ship. Due to the lack of preserved food samples, the exact source of infection could not be confirmed. Ships are not classified as collective dining facilities, leaving them in a management blind spot. Therefore, specialized guidelines, voluntary inspections by the operating entities, and continuous education for managers and staff are necessary.