Epidemiology of Emergency Medical Services-Assessed Mass Casualty Incidents according to Causes.

To effectively mitigate and reduce the burden of mass casualty incidents (MCIs), preparedness measures should be based on MCIs' epidemiological characteristics. This study aimed to describe the epidemiological characteristics and outcomes of emergency medical services (EMS)-assessed MCIs from multiple areas according to cause. Therefore, we extracted the records of all MCIs that involved ≥ 6 patients from an EMS database. All patients involved in EMS-assessed MCIs from six areas were eligible for this study, and their prehospital and hospital records were reviewed for a 1-year period. The EMS-assessed MCIs were categorized as being caused by fire accidents (FAs), road traffic accidents (RTAs), chemical and biological agents (CBs), and other mechanical causes (MECHs). A total of 362 EMS-assessed MCIs were identified, with a crude incidence rate of 0.6-5.0/100,000 population. Among these MCIs, 322 were caused by RTAs. The MCIs involved 2,578 patients, and 54.3% of these patients were women. We observed that the most common mechanism of injury varied according to MCI cause, and that a higher number of patients per incident was associated with a longer prehospital time. The highest hospital admission rate was observed for CBs (16 patients, 55.2%), and most patients in RTAs and MECHs experienced non-severe injuries. The total number of deaths was 32 (1.2%). An EMS-assessed MCI database was established using the EMS database and medical records review. Our findings indicate that RTA MCIs create a burden on EMS and emergency department resources, although CB MCIs create a burden on hospitals' resources.