1 Universal and Particular: The Language of Plague, 1348–1500

What disease or diseases caused the recurrent, demographically punishing epidemics that Europeans called plague? During the last twenty years a once prevalent historical consensus about causes and consequences of European plagues has dissolved, prompting new archival research as well as novel technological and interdisciplinary approaches to material evidence. The core debates about the history of plague are not, however, limited to scholars of medieval and early modern Europe. Molecular biologists over the last decade have determined that the organism that causes plague today, Yersinia pestis, is a relatively recent emergent pathogen descended from a significantly less lethal gastro-intestinal parasite, Yersinia pseudotuberculosis. Furthermore, fifty years ago microbiologists accepted a model of three different ‘‘biovars’’—biochemically different variants—of Yersinia pestis, which were tidily aligned to three historical pandemic waves: antiqua, mediaevalis, and orientalis. That synthesis, too, is seriously challenged. There are instead at least eight Yersinia pestis strains and four biovars, and all have emerged within the last 5000 to 20,000 years. This organism remains a likely perpetrator of the great plagues in Europe because all Yersinia pestis biovars can be extraordinarily lethal in human bodies. Most medievalists, including those who doubt that the Black Death and subsequent plagues could have been caused by Yersinia pestis, make a modern assumption that the Black Death indeed had some unique microbial cause. No one yet has argued in a sustained fashion that the plague was a ‘‘perfect storm’’ of many different epidemic infectious diseases, but one could. Nor has a radical scepticism emerged—for example, that the causes of each and every local or regional epidemic called peste/pestilentia by contemporaries need to be investigated separately, unrelated to other local contexts—but that, too, might be possible. If we would be truly rigorous, we cannot assume that a ‘‘plague’’ in one place was due to the same specific microbial cause as a pestilence in another locality, even