Plague is an infectious disease of humans and animals caused by the bacterium Yersinia pestis. During the Middle Ages millions of people in Europe died from plague, whose current mortality-if untreated-ranges from 50% to 90%. The plague has been a great protagonist in history because it has often been grimly present in the collective events of humans. Its plurisecular history, tied to the whole chain of ecological balance, has had a strong influence on the collective imagination on account of its sudden occurrence and unavoidable mortality. In the past, the passage from contagion to illness ended in death, as human remedies had no effect. The only way to conquer it was invoke the incorruptible spirit of a saint. Therefore, in the past, the major plague icons were saints to whom ordinary people attributed a fame for healing. More recently, many epidemic diseases have ceded place to biological weapons, and terrorists have become the modern icons of such a threatening reality. As a matter of fact, bioterrorism has become a great public health and infection control threat, and, among the number of potential biological agents, plague has assumed a key role.