Silk Road Atlas silk-road.xyz

Decline & Legacy

The Black Death and the Silk Road

The Black Death, the most destructive pandemic in recorded history, killed perhaps half the population of Europe and tens of millions more in Asia and North…

The Black Death, the most destructive pandemic in recorded history, killed perhaps half the population of Europe and tens of millions more in Asia and North Africa between 1346 and 1353. The disease, identified by modern microbiologists as the bubonic plague caused by Yersinia pestis, was unusual not only in the scale of its mortality but in the speed of its spread. It travelled from the steppes of Central Asia to the Crimea, and from there to every major port of the Mediterranean, in the space of less than five years. The vector was the trading networks of the late medieval world — the very networks that the Mongol Empire had created and that the Silk Road had sustained. The more I read about it, the more I think the Black Death is the most consequential single event in the history of the overland trade, even though the trade itself was its instrument.

The natural reservoir of the plague

The bacterium Yersinia pestis is a parasite of rodents, particularly of the species of ground squirrel and marmot that inhabit the steppes of Central Asia. The disease is transmitted between rodents by the bite of the rat flea, Xenopsylla cheopis. The bacterium persists in wild rodent populations in a relatively mild form, and erupts into the more lethal bubonic and pneumonic forms when ecological stress — drought, flooding, the death of the usual prey species — brings wild rodents into close contact with human settlements. I find it striking, in a way that the standard textbook account never quite gets across, that the disease is essentially a rodent disease that occasionally gets the wrong host.

This ecological chain explains why the plague repeatedly emerged from the steppes of Central Asia and why it spread so effectively along the trade routes. The political integration of Eurasia under the Mongol Empire created a continuous corridor of human settlement and trade from the Pacific to the Mediterranean — a corridor, as historians sometimes forget, that was also a continuous corridor of rodent settlement. The same infrastructure that moved silk, spices, and ideas also moved the rats, the fleas, and the bacterium.

The chronology of the pandemic

The Black Death of 1346–1353 was not the first outbreak of bubonic plague in the medieval world. The Plague of Justinian, in the sixth century CE, killed perhaps 50 million people in the Mediterranean basin and is treated in the article on the decline of the Silk Road as one of the factors that weakened the Byzantine Empire. The disease remained endemic in the rodent populations of the Middle East and Central Asia before the pandemic of the fourteenth century.

The pandemic of 1346–1353 appears to have begun in the steppes of Central Asia, possibly around Lake Issyk-Kul, in the late 1320s or early 1330s. From there it spread east into China, where it killed perhaps 25 million people, and west along the Silk Road into the Crimea. The traditional account holds that the disease reached the Crimean port of Kaffa in 1346, when the Mongol army besieging the city catapulted infected corpses over the walls — a story told by the Italian notary Gabriele de’ Mussi, who probably should not be trusted on the details. The story is probably apocryphal, but the disease did reach Kaffa, and from there it spread by Genoese and Venetian merchant galleys to Constantinople, to Alexandria, and to the ports of Italy: Messina, Pisa, and Genoa all went down in 1347.

The Black Death is, of Silk Road side effects, the worst — and the more I read the contemporary chronicles, the more I think the standard narrative understates how fast it travelled, which is itself a kind of indictment of the trade.

The plague cemetery at the now-closed mass burial site of the late 1340s in East Smithfield, London, is the largest single archaeological plague deposit in northern Europe. A DNA study of the East Smithfield remains in 2011 — Haensch et al. in Nature — confirmed Yersinia pestis as the cause, but the sample was small and the method, by the standards of 2026, was crude. The Smithfield site itself is no longer accessible, having been built over in the 1980s; the bones are in the Museum of London.

A personal note

The epidemiology of the Black Death is still debated, and the popular story (rats, fleas, the bacterium Yersinia pestis) is partly correct but probably not the whole story. Modern scholarship has begun to argue that the pneumonic and septicemic forms of the disease, transmitted directly between humans, may have been more important than the bubonic form transmitted by fleas. The reader should hold the textbook story with appropriate caution.

Further reading

  • Encyclopaedia of Islam, 2nd ed. (Brill), the relevant entry. Old but unequalled for the western Islamic world.
  • Encyclopaedia Iranica (Columbia), the relevant entry, for the Iranian sphere.
  • An article in the most recent volume of Silk Road Journal or Journal of Asian History.
  • A primary source in translation (named in the article above).
  • One recent monograph — see the suggested works in the other entries in this series.