Plague is a term applied randomly in the Middle Ages to all fatal epidemic diseases, but now restricted to an acute, infectious, contagious disease of rodents and humans, caused by a short, thick bacillus, Yersinia pestis. In humans, plague occurs in three forms: bubonic plague, pneumonic plague, and septicemic plague. Bubonic plague is the best-known form and is so called because it is characterized by the appearance of buboes, or enlarged, inflamed lymph nodes, in the groin or armpit or on the neck.

Bubonic plague is transmitted by the bite of any of numerous insects that are normally parasitic on rodents, and that seek new hosts when the original host dies. The most important of these insects is the rat flea Xenopsylla cheopis, which is parasitic on the brown rat. Untreated bubonic plague is fatal in 30 to 75 percent of all cases. The Black Death, the name later given to the plague, ravaged Europe between 1347 and 1351, taking a great toll of life.

Modern research confirms the estimate of the chronicler Jean Froissart that about one-third of the population died. Originating in China and Turkestan, the plague was transmitted to Europeans when a Kipchak army catapulted plague-infested corpses into the town. The Plague spread from the Mediterranean ports, affecting Sicily (1347); North Africa, Italy, Spain, and France (1348); Austria, Hungary, Switzerland, Germany, and England (1349); and Scandinavia and the Baltic lands (1350) (See Fig. 1).

There were recurrences in 1361-63, 1369-71, 1374-75, 1390, and 1400. In bubonic plague, the first symptoms are headache, nausea, vomiting, aching joints, and a general feeling of ill health. The lymph nodes of the groin or, less commonly, of the armpit or neck, suddenly become painful and swollen. The temperature, accompanied by shivering, rises to between 38. 3 and 40. 5 C (101 and 105 F). The pulse rate and respiration rate are increased, and the victim becomes exhausted and apathetic. The buboes swell until they approximate a chicken egg in size.

In nonfatal cases, the temperature begins to fall in about five days, and approaches normal in about two weeks. In fatal cases, death results in about four days. The purple color, which appears in all plague victims during their last hours, is due to respiratory failure; the popular name Black Death that is applied to the disease is derived from this symptom. Many preventive measures, such as sanitation, killing of rats, and prevention of the transport of rats in ships arriving from ports in which the disease is endemic, are effective in reducing the incidence of plague.

Famine, which reduces resistance to the disease, results in spread of plague. Individuals who have contracted the disease are isolated, put to bed, and fed fluids and easily digestible foods. Sedatives are used to reduce pain and to quiet delirium. During World War II, scientists using sulfa drugs were able to produce cures of plague; subsequently, streptomycin and tetracycline were found to be more effective in controlling the disease.

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