Black Death

The Black Death was one of the deadliest pandemics in human history. A pandemic is an epidemic that spreads over a very large area, across many countries at once. Between 1346 and 1353 a disease we now know as plague moved through the Black Sea region, the Mediterranean, Europe, the Middle East and North Africa. Estimates of the dead vary widely, but a common figure is that roughly a third or more of Europe’s people died, and some regions lost half or more.

People at the time did not call it the “Black Death.” Writers in Latin spoke of pestis or pestilentia (pestilence), epidemia and mortalitas—simply “mortality” or “the great death.” The name “black death” became popular through Swedish and Danish chroniclers in the fifteenth and sixteenth centuries and only entered English in the eighteenth century. The word “black” probably meant “dreadful” or “deadly,” not the colour of the victims’ skin.

The Black Death was not a single, one-time event. It was the first and most destructive wave of what historians call the second plague pandemic. After 1353 plague kept coming back to Europe and the Islamic world, again and again, for more than four hundred years.

Plague is caused by a bacterium named Yersinia pestis. It is named after Alexandre Yersin, a scientist who identified it during an outbreak in Hong Kong in 1894, more than five hundred years after the Black Death. The bacterium normally lives among wild rodents, such as marmots and some kinds of rats, and the fleas that feed on them.

When a flea drinks the blood of an infected animal, the bacteria can multiply inside the flea’s gut and block it. The starving flea then bites again and again, and it spits bacteria into each new bite. If the rodents die, their fleas look for new hosts—including humans. This is how plague jumps from animals to people.

Plague has three main forms. In bubonic plague, the most common, the lymph nodes in the groin, armpit or neck swell into painful lumps called buboes. In pneumonic plague the lungs are infected, and the sick person can pass the disease to others by coughing. In septicaemic plague the bacteria spread through the blood; this form was almost always fatal. Today the World Health Organization notes that plague can be treated with common antibiotics if it is caught early, but without treatment the pneumonic form can kill within a day.

In the fourteenth century, merchants carried silk, grain, spices, furs and enslaved people across the Black Sea and the Mediterranean. The Italian city-states of Genoa and Venice had trading ports on the northern shore of the Black Sea. One of them was Caffa, today’s Feodosia in Crimea. The traditional story says plague reached Europe from there around 1346–1347, while Caffa was besieged by the army of Jani Beg, khan of the Golden Horde.

From the Black Sea, ships carried the disease to Constantinople, where it arrived in the summer of 1347. By October 1347 Genoese galleys had brought it to Sicily; in January 1348 it reached Genoa, Venice and Marseille, and soon Pisa, from which it moved into northern Italy. By June 1348 it had struck France, Spain, Portugal and England. Between 1348 and 1350 it spread through Germany, Scotland and Scandinavia—a ship brought it to Norway in 1349—and it reached northern Russia in 1352 and Moscow in 1353.

At the same time, plague spread south and east. It reached Alexandria in Egypt by the autumn of 1347 and Cairo, then one of the biggest cities in the Mediterranean world, in 1348. It moved through Gaza, Damascus and Aleppo, arrived in Tunis by ship from Sicily, and was carried to Mecca by pilgrims. A few places with little trade—such as isolated Alpine villages—seem to have escaped the worst.

Eyewitnesses described swellings “as large as a common apple” or “an egg” in the groin or armpits, followed by dark spots on the skin, high fever and vomiting of blood. The Florentine writer Giovanni Boccaccio described these signs at the beginning of his book The Decameron. Most people who fell ill died within a few days.

The Sienese chronicler Agnolo di Tura wrote that fathers abandoned children and wives abandoned husbands, because the illness seemed to spread “through the breath and sight.” He wrote that great pits were dug for the dead, and that he buried his own five children with his own hands. So many died, he said, that people believed it was the end of the world.

Monks, nuns and priests were hit especially hard, because they cared for the sick and gave them the last rites. In many places there were not enough gravediggers, and the dead were buried in mass graves. Some of those graves, like the one at East Smithfield in London, have been excavated by archaeologists, and the bones have taught scientists a great deal about the disease.

The Black Death did not strike a healthy, stable world. Europe had already suffered the Great Famine of 1315–1317, and many people were poorly fed. Historians of the “crisis of the late Middle Ages” point to a combination of climate change, crop failures, war—including the Hundred Years’ War between England and France—and economic strain. Malnutrition may have weakened people’s resistance to disease.

The thirteenth and early fourteenth centuries were also a period of intense long-distance connection. The Mongol Empire and its successor states, including the Golden Horde on the steppes north of the Black Sea, linked the grasslands of Central Asia with Mediterranean trade. Genoese and Venetian merchants held ports such as Caffa and Tana. These networks moved goods, people and animals—and, it seems, the plague bacterium—over great distances.

The siege of Caffa became the most famous part of the story. The Italian notary Gabriele de’ Mussi wrote that the besieging army, suffering from plague, catapulted corpses over the walls, and that fleeing Genoese then spread the disease. This account is often called an early case of biological warfare. Historians, however, note that de’ Mussi was not present, that his story conflicts with other evidence from the Black Sea region, and that rats and fleas crossing siege lines—or grain shipments restarted after the war—could explain the spread just as well.

There are no exact figures. No census had been taken in England, for example, between the Domesday Book of 1086 and the poll tax of 1377, and most European estimates are extrapolated from partial records such as lists of clergy, tax registers and wills. Scholarly estimates of mortality in Europe therefore range from about 25% to 60%. The historian Ole Jørgen Benedictow has argued for a Europe-wide death rate of around 60%, while others favour figures near a third to a half.

Local numbers show the scale. Florence, which had perhaps 110,000–120,000 people in 1338, had about 50,000 in 1351. Half of Paris’s population of around 100,000 is said to have died. At least 60% of the people of Hamburg and Bremen perished. In Cairo, between a third and 40% of the inhabitants may have died within eight months, and Egypt as a whole lost around 40% of its people.

The impact was uneven. A 2022 study of pollen records from across Europe traced changes in farming to estimate population loss. It found signs of severe decline in places such as Scandinavia, France, western Germany, Greece and central Italy, but continued agricultural growth in parts of central and eastern Europe, Iberia and Ireland. Such research warns against assuming that every region suffered equally.

Unable to explain the disease, many Europeans looked for meaning and for someone to blame. The medical faculty of the University of Paris blamed a conjunction of planets that had corrupted the air. Many believed the plague was God’s punishment for sin. Groups of flagellants walked from town to town in 1349, whipping themselves in public to show repentance. Pope Clement VI condemned the movement in a bull of 20 October 1349.

The darkest response was violence against Jews, who were falsely accused of poisoning wells. Some were tortured into “confessing.” The first massacre linked to the plague took place in Toulon in April 1348; violence followed in Barcelona and other Catalan cities. In 1349 massacres spread through the Holy Roman Empire and beyond. In Strasbourg, around 2,000 Jews were burned on 14 February 1349—before the plague had even reached the city. The Jewish communities of Frankfurt, Mainz, Cologne, Worms, Speyer and many other towns were destroyed. By 1351, according to one estimate, 60 major and 150 smaller Jewish communities had been wiped out.

Clement VI issued two bulls in 1348 declaring that Jews could not be the cause, since the plague also killed Jews and struck places where no Jews lived; his physician Guy de Chauliac supported this view. But papal protection was weak outside Avignon, and some rulers profited from seizing the property of murdered Jews. Many survivors fled east, where King Casimir III of Poland offered refuge—one reason why eastern Europe became a great centre of Jewish life for the following six centuries. Lepers, foreigners, beggars and others were also targeted in some places.

The Black Death is often told as a European story, but it struck the Mamluk Sultanate of Egypt and Syria, North Africa and Arabia just as hard. In Cairo the young sultan an-Nasir Hasan fled the city; the Nile was said to be choked with corpses. The historian al-Maqrizi later described the endless work of gravediggers and funeral washers. Plague returned to Cairo more than fifty times over the next century and a half.

Muslim scholars and physicians debated how to respond. Some warned against trying to escape or treat a disease sent by God; others recommended preventive measures and drew, like European doctors, on ancient Greek medical writings. Arab historians such as Ibn al-Wardi and al-Maqrizi believed the pestilence had come from the lands of the Mongols in the east.

Two famous North African writers lived through it. The traveller Ibn Battuta was in Syria in 1348 as the plague spread, and on his return home he found Marrakesh almost empty. The historian Ibn Khaldun, then a teenager in Tunis, lost both his parents and many of his teachers; some scholars think this experience shaped his later reflections, in the Muqaddimah, on the rise and decline of societies and cities.

With so many dead, labour became scarce while land became plentiful. Workers could demand higher wages, and in some places rents collapsed. Landowners tried to hold on to tenants by turning labour services into money rents. Rising prices, however, meant that many wage earners did not immediately become better off; historians still debate how quickly real wages rose.

Rulers tried to freeze the old order by law. In England, Edward III issued the Ordinance of Labourers in 1349, and Parliament followed with the Statute of Labourers in 1351. These laws tried to fix wages at pre-plague levels, forced able-bodied people to work, and limited their freedom to move in search of better pay. The tension they created, together with war taxes, contributed to the Peasants’ Revolt of 1381 in England.

Many historians argue that the Black Death weakened serfdom in western Europe and helped reshape the relationship between lords and peasants, although the outcome differed from region to region. It also changed the Church: many parishes lost their priests, and smaller monasteries closed. In the long term, Europe’s population did not regain its early fourteenth-century level until the sixteenth century.

The plague left deep marks on literature and art. Boccaccio’s Decameron, probably written between 1348 and 1353, is framed by the epidemic: ten young people flee plague-stricken Florence to a villa and tell one hundred stories over ten days. Petrarch, who lost many friends, wrote that “happy posterity” would think his testimony a fable; years later he lamented to Boccaccio that the evil had never ceased.

Religious life changed too. Some historians describe an initial “religious paralysis” followed by a more personal, emotional devotion: new confraternities and guilds, devotion to the wounds of Christ and to the Virgin, and rich donations to churches. Art historians have also linked the plague years to a stronger focus on death and mortality in late medieval art, although such themes had several causes, not only the plague.

One lasting legacy was public health. In 1377 the city-state of Ragusa (modern Dubrovnik) required newcomers from plague areas to wait thirty days in isolation; the period was later extended to forty days, and the Italian word quaranta (“forty”) gave us the word “quarantine.” Cities gradually developed health boards, plague hospitals and rules for trade and travel during outbreaks.

For a long time many accounts claimed that the Black Death began in China and travelled west along the Silk Road. That view is now strongly contested. Scholars of the Yuan and Ming periods have found no specific evidence of a plague pandemic in fourteenth-century China, even though China’s population fell sharply between 1340 and 1370; war and famine may explain much of that decline. Others, such as Ole Benedictow, have argued for a source in the plague reservoirs near the Caspian Sea, and John Norris suggested Kurdistan. Monica Green has proposed that several lineages of Yersinia pestis spread in different directions, which could explain why the evidence looks different in different regions.

The most important recent evidence comes from the Chüy Valley near Lake Issyk-Kul in modern Kyrgyzstan. There, Christian (Church of the East) gravestones with Syriac inscriptions record a spike of deaths from “pestilence” in 1338–1339. In 2022 a team led by Maria Spyrou published ancient DNA from seven individuals buried at the Kara-Djigach and Burana cemeteries in Nature. They recovered Y. pestis genomes and identified the strain as the most recent common ancestor of the great diversification of plague lineages associated with the pandemic—supporting an early fourteenth-century source in central Eurasia, in the wider Tian Shan region.

This finding does not settle every question. It shows where the ancestral strain was circulating shortly before 1346, but not exactly how and when the bacterium travelled from the Tian Shan to the Black Sea, or whether it passed through other regions first. The debate now combines genetics with ecological models of rodent reservoirs, climate data and close reading of written sources in Latin, Greek, Arabic, Persian, Syriac and Chinese.

For much of the twentieth century some scholars doubted that the Black Death was plague at all. They pointed to its astonishing speed, its spread in cold northern climates and the lack of archaeological evidence for mass rat deaths, and proposed that another disease might have been responsible. The debate was largely settled by ancient DNA. In 2010 Haensch and colleagues detected Y. pestis in tooth pulp from mass graves across Europe, and in 2011 Bos and colleagues published a draft genome from the East Smithfield cemetery in London, showing that the Black Death strain is ancestral to most modern strains.

What remains debated is how the disease spread. The classic model, developed after the 1890s in India, runs from black rats to rat fleas to humans. Some researchers argue that human fleas and body lice, or direct person-to-person spread of pneumonic plague, better explain the speed and seasonal pattern recorded in written sources. Others stress that many kinds of animals, not only rats, may have been involved. No single alternative has won general acceptance, and different mechanisms may have dominated in different places.

Written sources need careful handling. Chroniclers often exaggerated numbers or borrowed literary models: John VI Kantakouzenos modelled his description on Thucydides’ account of the plague of Athens, and Froissart’s claim that “a third of the world died” may echo the Book of Revelation. Historians therefore cross-check chronicles with tax records, manorial court rolls, wills, clergy lists, archaeology and environmental data such as pollen. The name “Black Death” itself is a later label, and modern scholarship increasingly studies the pandemic as a trans-regional event rather than a purely European one.