How is a "mass casualty incident" defined?

A "mass casualty incident" is defined as an event where the number of casualties exceeds the available local medical resources to manage effectively. This situation typically arises in disasters or large-scale emergencies, such as natural disasters, terrorist attacks, or major accidents, where the volume of patients exceeds what hospitals and emergency services can handle with their existing personnel, equipment, and supplies. This definition emphasizes the critical need for a coordinated response that often involves multiple agencies and can include strategies like establishing triage systems and deploying additional resources from other areas to assist in the care of patients.