Which of the following would be considered a mass casualty incident (MCI)?

In the context of emergency response, a mass casualty incident (MCI) is defined by the number of patients and the resources required to manage their care effectively. Option D asserts that a call where available resources are insufficient constitutes an MCI, which is accurate because it highlights a key characteristic of such incidents: the demand for medical attention exceeds the capacity of the responding services to provide adequate care.

MCIs can result from various scenarios such as natural disasters, large-scale accidents, or mass shootings, where multiple casualties occur simultaneously. In these situations, first responders must quickly assess the situation and prioritize care, often using triage systems to manage the overwhelming number of patients. When available resources—such as personnel, equipment, and ambulances—are inadequate to address the needs of all victims, it is a clear indication of an MCI.

While other options speak to various elements of emergency responses, they do not capture the essential aspect of an MCI: that the resources available cannot meet the immediate needs posed by the incident. For instance, having at least two patients or multiple vehicles does not inherently define a situation as a mass casualty incident unless it also results in a resource strain. Similarly, a lack of tiered response might complicate the incident but does not