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The Black Death


The Black Death

A small mass burial pit, from the Black Death cemetery, East Smithfield, London, view looking west.

MOLA / Contributor/ Hulton Archives/ Getty Images

Summary of the Black Death

The Black Death was an epidemic which spread across almost all of Europe in the years 1346 – 53; the plague killed over a third of the entire population. It has been described as the worst natural disaster in European history.

What Was the Black Death?

There is no dispute that the “Black Death”, otherwise known as the “Great Mortality”, or simply “The Plague”, was a trans-continental disease which swept Europe and killed millions during the fourteenth century. However, there is now argument over exactly what this epidemic was. The traditional, and most widely accepted, answer is the Bubonic Plague, caused by the bacterium Yersinia Pestis, which scientists found in samples taken from French plague pits where bodies were buried.

Yersinia Pestis was spread through infected fleas which lived first on black rats, a type of rat which is happy to live near humans and, crucially, on ships. Once infected, the rat population would die off, and the fleas would turn to humans, infecting them instead. After three to five days of incubation the disease would spread to the lymph nodes, which would swell into large-blister like ‘buboes’ (hence ‘bubonic’ plague), usually in the thigh, armpit, groin or neck. 60 - 80% of those infected would die within another three to five days. Humans fleas, once blamed quite heavily, in reality contributed only a fraction of cases.


The plague could turn into a more virulent airborne variant called Pneumonic plague, where the infection spread to the lungs, causing the victim to cough up blood which could infect others. Some people have argued this aided the spread, but others have proved it wasn’t common and accounted for a very small amount of cases. Even rarer was a septicaemic version, where the infection overwhelmed the blood; this was nearly always fatal.

When Was the Black Death?

The main instance of the Black Death was between 1346 to 1353, although the plague returned to many areas again in waves during 1361-3, 1369-71, 1374-75, 1390, 1400 and after. Because extremes of cold and heat slow the flea down, the bubonic version of the plague tended to spread during the spring and summer, slowing right down during winter (the lack of many winter cases across Europe is cited as further evidence the Black Death was caused by Yersinia Pestis).

Where did it spread?

The Black Death originated in the north-west shores of the Caspian Sea, in the land of the Mongol Golden Horde, and spread into Europe when the Mongols attacked an Italian trading post at Kaffa in the Crimea. Plague struck the besiegers in 1346 and then entered the town, to be carried abroad when the traders hurriedly left on ships the next spring. From there the plague travelled rapidly, through rats and fleas living onboard ships, to Constantinople and other Mediterranean ports in the thriving European trade network, and from there through the same network inland.

By 1349 much of Southern Europe had been affected, and by 1350 the plague had spread into Scotland and north Germany. Overland transmission was again either via rat or fleas on people / clothing / goods, along communication routes, often as people fled the plague. The spread was slowed by cool/winter weather, but could last through it. By the end of 1353, when the epidemic reached into Russia, only a few small areas such as Finland and Iceland had been spared, thanks largely to only having a small role in international trade. Asia Minor, the Caucasus, the Middle East and North Africa also suffered.

Death Toll

Traditionally, historians accept that there were variations in the rates of mortality as different areas suffered slightly differently, but roughly one third (33%) of Europe’s entire population succumbed between 1346 – 53, somewhere in the region of 20-25 million people. Britain is often quoted as losing 40%. Recent work by O. J. Benedictow has produced a controversially higher figure: he argues that mortality was surprisingly consistent across the continent and that in reality three fifths (60%) perished; roughly 50 million people.

There is some dispute about urban verses rural losses, but in general the rural population suffered as heavily as the urban ones, a key factor given that 90% of Europe’s population lived in rural areas. In England alone deaths rendered 1000 villages unviable and survivors left them. While the poor had a higher chance of contracting the disease, the rich and noble still suffered, including King Alfonso XI of Castile, who died, as did a quarter of the Pope’s staff at Avignon.

Medical Knowledge

The majority of people believed the plague was sent by God, largely as a punishment for sins. Medical knowledge in this period was insufficiently developed for any effective treatments, with many doctors believing the disease was due to ‘miasma’, the pollution of the air with toxic matter from rotting material. This did prompt some attempts to clean up and provide better hygiene – the King of England sent a protest at the filth in London’s streets, and people were afraid of catching the illness from affected corpses – but it didn’t tackle the root cause of rat and flea. Some people seeking answers turned to astrology and blamed a conjunction of the planets.

“End” of the Plague

The great epidemic ended in 1353, but waves followed it for centuries. However, medical and governmental developments pioneered in Italy had, by the seventeenth century, spread across Europe, providing plague hospitals, health boards and counter-measures; plague consequently decreased, to become unusual in Europe.
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