What best defines a mass-casualty incident (MCI)?

A mass-casualty incident (MCI) is characterized by a situation where the number of patients exceeds the resources available for treatment and transport. This definition underscores the operational challenge faced by emergency responders when they cannot effectively manage all affected individuals with their existing capabilities. In an MCI, the sheer volume of patients often requires a coordinated response from multiple agencies and an effective triage system to prioritize care for those in the most critical need.

The essence lies in recognizing that an incident becomes mass-casualty not merely due to arbitrary numbers or the severity of injuries, but specifically when the demands placed on emergency services surpass their capacity to respond adequately. This definition trains responders to anticipate and prepare for the strain on personnel, equipment, and facilities during such incidents, ensuring that they can mobilize additional resources and manage the situation more effectively.