Preface

The Plague, also known as bubonic plague, pestis or the Black Death, was an acute, severe infection caused by the bacillus Yersina pestis (formerly known as Pasteurella pestis, now named after Yersin who first described it in 1894). This bacillus is primarily an internal parasite of wild rodents, such as rats, mice and squirrels, for whom the resulting illness may be acute, subacute, or chronic. It is carried to man by fleas deserting dying or dead animals, in search of nourishment. It may enter the bloodstream directly as the flea bites the host, or indirectly through contact between fleas' excrement, and scratches or lesions on the skin. Massive human epidemics have occurred. The most infamous was the Black Death of the Middle Ages. More recently, infections have occurred sporadically but have tended to be limited.

Modern science has identified two main types of plague; bubonic plague and primary pneumonic plague. Bubonic plague was named after buboes (enlarged lymph nodes) which first become visible during, or shortly after, the fever. This was the most common form of the Plague and the incubation period varied from a few hours to 12 days, (but generally 2 to 5 days). The onset was abrupt and often associated with chills; the temperature rapidly rose to 39.5 to 41 C (103 to 106 F). Occasionally, a primary sore appeared at the bite site, varying from a small spot to a large suppurating ulcer. These often changed in colour from orange to black, or blue or purple, and, of all the different signs of the Plague, these were the easiest 'tokens' of recognition. The sufferer was often restless, delirious, confused and uncoordinated. Most deaths occurred from blood poisoning in 3 to 5 days. Some victims however, took a month or so to die. Until the advent of antibiotics, the mortality rate was generally between 60 and 80%. This form of the disease spread though a community very rapidly, thriving in a humid and warm climate; which provided ideal conditions for fleas to breed and flourish. In Europe, the months between July and October normally nurtured optimum infestation. However, fleas have been known to survive through winter in warm 'ecosystems'. For example, until the Eighteenth Century, the supports of floors and roofs in wooden, or wattle and daub buildings, harboured the nests of black rats. (Brown and grey rats not appearing until the Eighteenth Century).

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