Late Middle Ages

How did the Black Death spread across Europe?

The Black Death is sometimes described as having “swept” across Europe, as if the disease were carried by an invisible wind. The image is misleading. The Black Death spread through the same channels by which medieval people, goods, and ideas moved: along the trade routes, the pilgrimage paths, the shipping lanes, and the war roads of the fourteenth century. To follow the pandemic is, in this sense, to follow the medieval economy and the medieval world system in action. The disease moved at the speed of medieval transport, and the medieval economy was the perfect medium for the spread of a contagious disease.

The clinical forms of the disease are explained in Bubonic vs pneumonic plague: what was the difference?, and the medical response is treated in Medieval medical responses to the Black Death. The recurring waves of plague that followed the original pandemic are discussed in Why did the plague return in waves?. The broader context of the pandemic is set out in the overview of the Black Death.

From the Steppe to the Galley

The most widely accepted modern theory locates the initial outbreak of the Black Death in the grasslands of Central Asia in the 1330s. The genetic work published in Nature in 2010–2011 by Mark Achtman and others, summarised in Benedictow’s The Black Death 1346–1353 (2004), traced the medieval strain of Yersinia pestis to a common ancestor that circulated in the rodent population of Central Asia in the early fourteenth century. From there, the disease moved east and west along the trade routes of the Mongol world, reaching the Black Sea port of Caffa (modern Feodosia in Crimea) by 1346.

Caffa was a Genoese trading colony on the northern coast of the Black Sea, a hub of the medieval silk and spice trade, and it was under siege by the Mongol army of Janibeg at the time of the outbreak. According to a famous account by the chronicler Gabriele de’ Mussis of Piacenza, the Mongols catapulted the bodies of plague victims over the city walls in an act of biological warfare. The story is disputed. Some historians, including Ole J. Benedictow, take the story at face value; others, including Samuel K. Cohn Jr. in The Black Death Transformed (2002), regard it as a later addition to the chronicle. Whether or not the story is true, plague broke out among the besieged, and the Genoese merchants, desperate to escape, took to their galleys and fled.

The departure of the Genoese galleys from Caffa in the spring of 1347 was the moment at which the Black Death became a European pandemic. The galleys carried the disease to Constantinople, to the Greek islands, to the ports of southern Italy, and to the western Mediterranean. The historian John Hatcher, in The Black Death: A Personal History (2008), describes the moment as “the hinge of the pandemic”: the moment at which a regional outbreak became a continental catastrophe. The hinge was a Genoese galley.

The Mediterranean in 1347–1348

In October 1347, twelve Genoese galleys from Caffa arrived at the Sicilian port of Messina. The crews were already sick. The port authorities, alarmed by rumours of a mysterious pestilence in the East, ordered the galleys out of the harbour, but it was already too late. The disease spread to the local population within days, and from there to the rest of Sicily, to Pisa, to Genoa, to Marseille, and to Barcelona. By the spring of 1348, every major port in the western Mediterranean was affected. From the ports, the disease moved inland, following the trade routes to Florence, Rome, Paris, and the great fairs of Champagne.

The Mediterranean was a single integrated system of trade, and the disease moved through it with terrifying speed. Genoese, Venetian, Pisan, and Catalan merchants carried goods, letters, and rats between the great commercial cities, and they carried the plague as well. The first European city to be hit was, almost certainly, Messina, but the disease appeared almost simultaneously in Pisa and Marseille, both of which had close trading contacts with Sicily and with the Genoese colonies in the East.

The Tuscan cities were affected in the spring of 1348. Pisa lost perhaps half its population. Florence lost perhaps 50,000 to 60,000 of its 90,000 inhabitants, according to the chronicler Marchionne di Coppo Stefani. Siena lost perhaps two-thirds of its population, according to the chronicler Agnolo di Tura: “It was as if the world had come to an end,” Agnolo wrote, “and there was no one to be found who would bury the dead.” Rome was affected in the summer of 1348, and the papal court at Avignon in the autumn. The king of France, Philip VI, ordered a series of public fasts and processions, and the pope, Clement VI, consecrated the Rhône in April 1348 in an attempt to halt the spread of the disease. The Rhône was the principal route by which the disease moved northward from Marseilles to Avignon and beyond, and the consecration is a striking example of the religious response to a disease that was, in fact, transmitted by the trade routes of the medieval economy.

France, the Low Countries, and England

From Marseille, the disease moved up the Rhône valley to Avignon, where Pope Clement VI sat on the throne of the papacy, and then north to Paris, Bordeaux, and the Channel ports. The court of the pope, the great university of Paris, and the wine trade of Bordeaux were all affected within months. The court of Clement VI, in Avignon, lost perhaps half its members; the university of Paris lost many of its doctors and scholars; the city of Paris lost perhaps half its population.

The disease reached Normandy and Brittany in the late summer of 1348 and crossed the Channel to England in the late spring of 1349. The first English outbreak is usually identified at the southwestern port of Melcombe Regis in June 1348, but the disease may have arrived in London slightly earlier, perhaps carried by Channel-crossing vessels. The great Benedictine monastery of Croyland in the Lincolnshire fens lost more than half its monks to the disease in the summer of 1349, an event recorded in a famous letter by the abbot. Norwich, the second city of England at the time, lost perhaps half its population. London lost perhaps two-thirds of its inhabitants. The disease then spread to Scotland, Wales, and Ireland, although the highlands of Scotland and the wilds of Ireland were less affected than the densely settled lowlands.

The English records of the outbreak are unusually rich, and they provide some of the most important evidence for the spread of the disease. The parish records of mortality, the Calendars of Patent Rolls, the chronicles of Henry Knighton and Thomas Walsingham, and the famous letter of the abbot of Croyland are the principal sources. The historian Rosemary Horrox, in The Black Death (1994), has translated and edited the principal English sources, and the historian John Hatcher, in Plague, Population and the English Economy 1348–1530 (1977) and The Black Death: A Personal History (2008), has used the records to reconstruct the spread of the disease in a single village. The English experience is, in this sense, one of the most thoroughly documented in Europe.

The Empire, the Baltic, and the Holy Roman Empire

The disease reached the cities of the Holy Roman Empire in 1348–1349, and from there it moved along the Rhine and the Danube into Austria, Bohemia, and Hungary. The kingdom of Bohemia, under the rule of Emperor Charles IV, attempted to keep the disease out by sealing its borders in 1348. The sanitary cordon held for two years — an early example of a successful cordon sanitaire — but the cordon was broken in 1351, and the disease entered Prague and the Bohemian cities. The case of Bohemia is interesting because it shows that the medieval state was capable of organising an effective public health response, and that the response could work, at least for a time.

From Germany, the disease moved north to the Baltic ports of Lübeck, Hamburg, and Danzig, and from there it was carried by the great cogs of the Hanseatic League to Scandinavia. Bergen, Stockholm, and the Danish cities were all affected by the autumn of 1349. The pattern of spread in northern Europe was closely linked to the pattern of trade. The Hanseatic ports, the great marts of Novgorod and Bergen, and the inland cities of the Baltic plain all received the disease within a few months of one another. The disease then moved into the Scandinavian interior, but the thinly populated highlands of Norway and the forests of Sweden were less affected than the dense commercial cities of the southern Baltic.

The German experience is also one of the most important for the social history of the plague. The pogroms of 1348–1350, which began in the towns of the Upper Rhine, were a direct consequence of the spread of the disease into the cities of the Empire, and the pattern of persecution is examined in Jewish persecution and the spread of plague. The pattern of the response — the wave of flagellant processions, the public fasts, the oaths sworn by the towns to maintain permanent sanità boards — is the subject of The flagellant movement and the Black Death.

The Rat, the Flea, the Grain Sack

The Black Death did not, of course, “know” the medieval trade routes. It was carried along them by the rats and fleas that infested medieval ships, warehouses, and houses. The black rat (Rattus rattus) was a commensal species that had lived in close association with humans for centuries. The plague bacterium lived primarily in the rat population, and the rat flea (Xenopsylla cheopis) transmitted it from rats to humans, usually through a bite. The fleas were happy to feed on humans when their preferred rat hosts died, and the bacterium could also be transmitted directly from person to person in the pneumonic form of the disease.

The medieval household was, in modern terms, an open ecosystem in which rats, fleas, and humans lived in close and continuous contact. Granaries, kitchens, bakeries, stables, and warehouses all harboured rats. Ships’ holds were particularly conducive to the spread of plague, since the cramped conditions, the presence of grain stores, and the close contact between sailors and rats created ideal conditions for transmission. The trade routes of the medieval world were thus, in this sense, the trade routes of the rats.

The historian Mark Bailey, in his introduction to The Cambridge History of the Black Death (2015), has emphasised the role of the grain trade in the spread of the disease. The major grain-exporting regions of the European plain — Poland, the Baltic, and the Ukraine — provided the grain that fed the cities of western Europe, and the grain was carried by the same ships that carried the rats. The grain trade is, in this sense, one of the principal mechanisms by which the disease was carried from the East to the West. The mechanism is also one of the reasons why the outbreaks of 1348 and 1349 followed the major trade routes so closely.

Why So Fast?

The speed of the Black Death’s spread is one of the most striking features of the pandemic. The disease crossed the Mediterranean, the Alps, the Rhine, and the English Channel within roughly two years. It reached the Baltic within three, and it reached the Russian steppes within four. The speed can be explained in part by the speed of medieval transport — fast ships, well-organised caravans, and the rapid movement of armies and pilgrims — and in part by the fact that the disease was being carried along multiple routes simultaneously. Once the disease had reached a major port, it could be carried inland in a matter of days by merchants, officials, and travellers.

The medieval economy was, in this sense, the perfect medium for the spread of a contagious disease. The trade routes were dense, the cities were large, and the population was mobile. The disease moved at the speed of the medieval economy, and the medieval economy moved quickly. The Black Death was, in a real sense, the first European crisis — the first event in European history that affected every corner of the continent within a single generation. It was also a reminder that the medieval world was more connected, more integrated, and more interdependent than is often supposed.

References

  • Benedictow, Ole J. The Black Death 1346–1353: The Complete History. Boydell Press, 2004.
  • Hatcher, John. The Black Death: A Personal History. John Murray, 2008.
  • Horrox, Rosemary, trans. and ed. The Black Death. Manchester University Press, 1994.
  • Bailey, Mark, ed. The Cambridge History of the Black Death. Cambridge University Press, 2015.
  • Cohn, Samuel K. Jr. The Black Death Transformed: Disease and Culture in Early Renaissance Europe. Oxford University Press, 2002.