The Plague, which occured several times throughout history, exists in three different forms. It has a variety of modes of transmission and symptoms which make it all the more deadly. It was not to be called the Black Death until a century later. At its height it was called The Pestilence or the Great Mortality.

The most common form, called bubonic, is characterized by the formation of egg-sized swellings at the site of an infected flea bite, usually located in the armpits, groin or neck. Acute agonizing pain accompanies these growths. Next, hemorrhaging under the skin occurs, causing purplish blotches that frequently encircle the waist. Victims of Bubonic Plague die within four to six days of contracting the disease. The bubonic plague was the type that first appeared during the "Black Death" and it caused a majority of the deaths due to the plague.

A second form, pneumonic, occurs when the infection moves into the lungs, allowing the bacteria to be transmitted easily from person to person. A cough, a sneeze or the mere act of breathing sends death into the air. Symptoms include vomiting blood and skin ailments. When the pneumonic type developed, the plague reached a whole new level. Each of the forms were lethal, but the pneumonic form could strike with an abruptness that added to the terror the disease evoked.

In septicemia, the third type of the plague, massive numbers of the bacilli enter the bloodstream. A victim's body virtually explodes with the disease. A rash appears within hours, and death occurs within a day, even before rashes or abrasions occur on the skin. This is the most deadly, rare, and painful version of the plague.

All diseases have their own methods for creating misery, but the plague brought with it a unique ability to degrade, disgust and destroy its victims. Whatever form a victim contracted, everything about the plague was disgusting, so that the sick became objects of revulsion rather than of pity. Angelo di Tura, a chronicler of Siena, described the atmosphere as one in which "Father abandoned child, wife husband, one brother another for this plague seemed to strike through breath and sight, so they died." It was not unusual to hear of people going to bed in health and never wakening; of doctors catching the illness at the bedside and dying before the patient; and of persons, who during the course of normal conversation, dropped dead in mid-sentence.