A Plague of Plagues: The Problem of Plague Diagnosis in Medieval England

Beginning in 1348, an epidemic of massive proportions struck Western Europe, spreading from Italy northward. Contemporary accounts referred to it as the pestis or a pestilentia generali, terms translated as plague. Although it has generally been accepted that this great epidemic of the mid-fourteenth century, often referred to as the Black Death, was the plague, this view has been challenged by scholars from various disciplines.

Although the term plague has, at times, been used to describe an epidemic of great magnitude, this article will use it in the biological sense. Alexander Yersin identified the bacterial agent of the disease during the Hong Kong epidemic of 1894. First labeled Pasteurella pestis, the bacteria would later be renamed Yersinia pestis in Yersin's honor. There are three related Yersinia species: Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia entercolitica. Only the first one poses a major threat to humans. Dating from the early nineteenth century, scholars have equated the great pestilence of the fourteenth century with the Black Death and, by extension, a plague. In this case, the term plague was merely a label for a disease of extreme virulence.¹

In one sense, the question of whether the Black Death was Yersinia pestis or some other ailment is a moot point, because only laboratory testing can provide conclusive evidence for a clinical diagnosis. The only available evidence derives from chronicles and medical treatises often fragmentary and even misleading; a few mortality records, often oblique in origin; and scant dna evidence.

In another sense, the question of whether the outbreak in the fourteenth century was indeed the plague is relevant to understanding the impact of disease on medieval society and to understanding the potential impact of the plague today. The publication of three recent works reopens the question of plague diagnosis in a fashion that warrants re-examination of the evidence.²

This article examines this vexed question using England as a case study—England having been the focus of much of the debate concerning the viability of the plague diagnosis. This approach presents both difficulties and advantages concerning evidence. It takes into account medieval descriptions of the plague; early twentieth-century, pre-antibiotic plague epidemics; and various scientific analyses of plague, including efforts to analyze medieval dna. This interdisciplinary perspective produces better results than a study centered on history alone.

Doubts concerning the diagnosis of plague for the great epidemic of the fourteenth century center on the following points of contention: timing—the speed with which the epidemic spread; mortality rate—the percentage of the population that died during the epidemic, in toto and by gender; seasonality—the months of the year that exhibited the highest mortality; the agents of infection—the manner in which the disease spread; and symptoms—the extent to which the indications at the time match those of Yersinia pestis. Critics of the plague diagnosis advance arguments concerning these points to show that the disease of late medieval England could not have been the plague because the evidence does not fit the nomenclature of the plague in the twentieth century.

This study falls into the pro-plague camp, arguing that the epidemic that spread across mid-fourteenth-century England was Yersinia pestis, though with an important caveat: The plague did not by itself cause the high mortality in mid- and late fourteenth-century England. No one disease alone could have caused that mortality rate. Plague, however, played a major role in the large number of deaths.

The Progress of the Plague

Although not all of the chronicles agree, the Black Death seems to have arrived in England at the end of June 1348 through the port of Melcombe Regis in Dorset. An entry point in the southwest, probably connecting with France, makes the most sense, but both the Anonimalle Chronicle and the Eulogium Chronicon indicate that the plague arrived via Bristol, whereas Henry Knighton indicated that it was Southampton. The disease spread across the south of England, remaining in Hampshire in early 1349. It had reached London by November before moving north. Robert...