The History of the Black Death

Buboe on upper thigh of person with bubonic plague. This differs from the black death which was a Haemorrhagic Plague (so named because extensive haemorraging is an important symptom)

Swellings of the lymph glands (called buboes) are one feature of bubonic plague and, because these were also found in some victims of the Black Death, everybody in about 1900 leaped to the conclusion that bubonic plague was also responsible for all the plagues of Europe in the Middle Ages and this view has persisted for the whole of the twentieth century. However, the real diagnostic feature of the Black Death was the haemorrhagic red spots on the chest, which were called God’s tokens and were the result of bleeding from damaged blood vessels under the skin. Nobody compared the two diseases objectively and this view, based solely on the appearance of one symptom, was universally accepted without question. To distinguish clearly between the two diseases, we have named the disease that caused the Black Death haemorrhagic plague.

Bubonic plague is a disease of wild rodents in which the bacterium, Yersinia pestis is spread between them by infected fleas. Occasionally today it is transmitted to humans from peridomestic rats and there are some 1600 cases a year which are readily cured by antibiotics.

Evidence

To be able to refute unequivocally the belief that Yersinia pestis was the pathogen of the Black Death it is necessary to understand fully the complicated biology of bubonic plague. The key lies in the difference between susceptible and resistant rodent species. Susceptible species, like rats, die from the infection and an outbreak of human bubonic plague was often presaged by the appearance of hundreds of dead rats. Obviously an outbreak cannot be maintained for any length of time and bubonic plague cannot become endemic where all the local species are susceptible. There never have been any resistant wild rodents living in Europe and, consequently, it is impossible that persistent epidemics of bubonic plague could become established, even in the twentieth century when ships regularly brought infected rats into the ports.