Mass Casualty Incidents (MCIs) pose significant challenges to health care systems, especially regarding emergency preparedness and response. This study aims to analyze the epidemiological characteristics and burden of MCIs in Spain from 2014 to 2022, focusing on the type, frequency, and impact of these incidents on public health and emergency services.

A population-based retrospective observational study examined MCIs in Spain between January 2014 and December 2022. Data were collected from various emergency services. Incidents involving 4 or more victims requiring medical assistance and ambulance mobilization were included. The study categorized MCIs into 5 types: road traffic accidents, fires and explosions, chemical poisonings, maritime accidents, and others.

A total of 1618 MCIs resulting in 8556 victims were identified, averaging 15 (95% CI, 11-19) incidents per month, with 79% due to road traffic accidents and 13% to fires and explosions, which also had the highest average of 7.6 victims per incident. Despite maritime accidents comprising only 1.9% of incidents, they had the highest fatality rate. MCIs were more frequent on weekends, in January and July, and between 3:00 PM and 9:00 PM. The average response time was 38 minutes, with 35% of victims sustaining severe injuries.

Despite a slight decrease in annual MCIs from 2014 to 2022 in Spain, the trend is not statistically significant. The study highlights the need for a national registry and standardized data collection to enhance emergency preparedness and response planning and facilitate the reduction of the MCI burden.