Triad has been applied to the study of injury by scientists at the Centers
for Disease Control and Prevention (CDC). For injury, the agent is any one
of the five forms of physical energy: kinetic or mechanical energy, chemical
energy, thermal energy, electricity, and radiation. This energy is conveyed
to the host via a vector, such as a biting dog or snake, or its inanimate
counterpart, the vehicle. Examples of potential injury vehicles are crashing
automobiles and speeding bullets.