13 Facts About the Black Death

The pandemic of bubonic plague—later dubbed the Black Death—raged through Europe from 1347 to 1351 and wiped out between one-third and two-thirds of the entire population. But it wasn’t all bad: the calamity actually led to better literacy and labor conditions. Here are 13 facts about the Black Death.

Bubonic plague has affected humans for millennia.

Recent archaeological research has found evidence of bubonic plague in two Bronze Age skeletons uncovered in Russia, suggesting the disease has been around for thousands of years. The Justinianic Plague, which swept through the Mediterranean and Near East in the 6th century CE, is the first recorded pandemic of bubonic plague. (It coincided with the reign of Byzantine emperor Justinian, hence the name.) Historians consider the multiple waves of plague in the 14th century, later dubbed the Black Death, to be the world’s second plague pandemic.

Bubonic plague is a zoonotic disease.

The highly infectious disease is caused by a bacterium, Yersinia pestis, that infects rats and other small mammals as well as humans. It is spread by fleas that feed on the infected animals and carry the bacteria in its intestines. When their host rodents die from the disease, fleas look for a new source of food and move on to humans and livestock, transferring the deadly bacteria through their bites.

Bubonic plague is named after one of its primary symptoms.

One of the first symptoms of plague to appear are painful, swollen lymph nodes at the neck, groin, and armpit known as “buboes,” which give their name to the disease. As the illness progresses, sufferers experience headache, vomiting, and high fever, and their buboes secrete blood and pus. There was no viable treatment in the medieval period and most people with plague would be dead within seven days. Today, plague can be cured with antibiotics.

The Black Death originated in central Eurasia.

The episodes of disease that triggered the Black Death originated in central Eurasia. During the 1340s, the plague moved through India, Syria, Persia, and Egypt and decimated communities in its path before reaching Europe in 1347.

The Black Death was used as a biological weapon.

In 1347, the Mongol khan Janibeg was in the midst of a siege of Kaffa, a Genoese trading port in modern-day Crimea. He hoped to oust the Genoese merchants from the territory, but his own troops were greatly depleted by the Black Death and victory looked impossible. In a final act of vengeance, Janibeg’s army used a trebuchet (a sort of medieval catapult) to fling the plague-ridden bodies of his own soldiers into the walled city. The residents of Kaffa, already weakened by the siege, were soon overcome by disease.

The Black Death probably entered Europe through Messina, Sicily.

Rats live in proximity to humans and were usually present on the merchant ships that sailed from country to country, often spreading disease with them. Medieval folklore warned that if there were a lot of dead rats around, then disease and pestilence would follow.

Genoese ships carried trade goods—and unintentional cargoes of plague-infected rats—from Central Asia to the port city of Messina, Sicily, in 1347. The plague quickly spread through Europe, first engulfing the Italian peninsula and then moving on through France, Spain, and Germany. The epidemic reach England by 1349 and Scandinavia by 1350. Historians have traced how merchant ships drove the spread of plague: busy shipping ports, such as Kaffa, offered perfect opportunities for the pathogen to find new hosts and catch rides along the world’s major trade routes. As a result, the highest death tolls are estimated to have occurred in ports and large cities such as Venice and London.

It was not just a peasant’s disease.

Because it infects humans via fleas and rats, the Black Death has been mischaracterized as a “peasant’s disease” affecting only those who lived in less-than-hygienic environments. Yet the Black Death touched all sectors of society, from the very poor to the very rich. The number of high profile deaths from the plague included Joan, the favorite daughter of England’s King Edward III; Eleanor of Portugal, Queen of Aragon; King Alfonso XI of Castile; two archbishops of Canterbury, John de Stratford and Thomas Bradwardine; and the philosopher William of Ockham.

Members of a religious movement tried to halt the plague by whipping themselves.

Imagine how terrifying the Black Death must have seemed before anyone understood the germ theory of disease. Some people became convinced that the plague was a punishment sent by God and sought to halt its spread by taking part in public displays of penance.

Many joined the flagellant movement, which had existed in northern and central Europe since the mid-13th century but gained more followers amid the chaos of the Black Death. Groups of monks and religious devotees led processions through cities, towns, and villages while whipping themselves and each other and calling on observers to repent. The flagellation caused such gruesome injury (which, ironically, may have made the flagellants more susceptible to infections) that Pope Clement VI denounced the movement.

Quarantine was introduced during the Black Death.

While there was no understanding of germ theory in the Middle Ages, people did sense that the Black Death could be transferred from person to person. Officials imposed health regulations aimed at containing the disease. Plague doctors visited communities and told symptomatic families to stay in their homes or go to plague hospitals. Ships were prohibited from disembarking sailors for 30 days after arrival in ports, a method first used in Venice in 1347. The practice proved effective, and the wait was eventually extended to 40 days for each newly arrived ship. Quarantine derives from the Italian quaranta and Latin quadraginta, both meaning “forty.”

The Black Death came in waves.

The initial phase of the Black Death hit Europe in 1347 and rippled through the region until 1351—but this was not the end of the pandemic. The disease recurred in Europe several times over the next 50 years, in 1361–63, 1369–71, 1374–75, 1399, and 1400. These fresh attacks of plague were again carried into Europe by ships from Asia, spreading the disease along trade routes. More epidemics occurred in the 17th century, notably in London in 1665–66, when around a quarter of the city’s population died.

The world’s third plague epidemic emerged in Yunnan, China, in the mid-19th century, spreading quickly to Taiwan, Hong Kong, Japan, India, and farther afield. It killed 12 million people in India alone.

The cause of plague was not known until the Victorian era.

By the 1890s, medical knowledge had advanced sufficiently to identify the bacteria responsible for the bubonic plague. Researchers from multiple countries headed to Asia in the late 19th century to study the disease as it spread. In 1894, Japanese bacteriologist Kitasato Shibasaburō traveled to India and succeeded in identifying the bacterium; mere days later, French-Swiss bacteriologist Alexandre Yersin also isolated it. A controversy erupted over who would receive credit for the discovery. Many historians now consider the two researchers to be co-discoverers, but the microbe’s scientific name is still Yersinia pestis. (The genus Yersinia was established in 1944 in Yersin’s honor.)

The breakthrough allowed Yersin’s successor, Paul-Louis Simond, to test a hypothesis based on reports that thousands of dead rats in the streets seemed to accompany an outbreak of plague in people. “On the rats captured alive, and on the rats which had just died, the fleas were thicker than I have ever seen them,” he wrote. “We have to assume there must be an intermediary between a dead rat and a human. This intermediary might be the flea.” 

A simple experiment demonstrating that fleas transmitted plague from an infected rat to a healthy one proved Simond’s theory.

The 14th-century pandemic wasn’t called the Black Death until later.

In England, the Black Death was popularly known as “the pestilence,” and in much of the rest of Europe as “the plague” or “the great dying.” Elizabeth Penrose, in her 1823 book A History of England, dubbed the plague of 1347–51 the “Black Death”—a suitably terrifying name that stuck.

But even before then, 16th-century Danish and Swedish chronicles described a deadly plague in Iceland in 1402–03 as the “Black Death,” though no one is sure why. The chronicles were later translated into German and English and the description they used was retrospectively applied to the 14th-century plague in Europe.

The Black Death wasn’t all bad.

Despite the terrible death toll, in which an estimated 60 percent of Europe’s population died, the Black Death did lead to some positive social changes. The labor shortage following the pandemic had far-reaching effects, ultimately sparking a rise in wages and better conditions for the peasants who worked the land. These shortages also created an impetus to develop new labor-saving technologies, such as smaller, faster boats that needed fewer crew members, making exploration (and exploitation) of Asia and the Americas possible.

And, after many of the monks responsible for copying manuscripts perished in the plague, societies needed new ways to copy and distribute books—precipitating the invention of the printing press and encouraging the spread of ideas.

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