Trade Networks and the Black Death

By Bennett Sherry
Disease has always plagued human communities. One of the biggest epidemics in world history was started by one of the smallest animals and spread by trade networks in the world’s largest empire.

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A medieval painting of several worshippers carrying a model of Jesus on the cross. In front of them, three men hold up a red flag.

Spread the Word, but Cover Your Mouth

In 2008, up to 30 million computers were infected by the Conficker worm, one of the worst computer viruses ever. It caused billions of dollars in damages and disrupted government agencies and businesses all around the world. We like to think that more connection is good, that the more people talk to each other, the better the world will be. Today though, with a global Internet that connects billions of devices, viruses like Conficker can plague millions of people in minutes. Our connections help us to communicate, but they also make us vulnerable.

The Internet of the fourteenth century was the Silk Road. The Silk Road was less of a road than it was a network. Rather than thinking of it as a single route linking China to Europe, we should think of the Silk Road as a bunch of merchants and cities, trading posts and oases, ports and paths that were connected to each other by trade. In other words, think of it as the Silk Network, not the Silk Road. And like the networked Internet of the twenty-first century, ideas, information, goods, and money all traveled along the linkages of the Silk Network. But these long-distance trade connections, like the connected devices of our digital age, also allowed diseases to spread farther and faster than ever before. The worst of these was an outbreak of bubonic plague in the fourteenth century known as the Black Death.

Painting of many people, carrying wooden coffins, getting ready to bury plague victims. Most people wear sad expressions on their faces.

The people of Tournai (a city in present-day Belgium) bury plague victims, 1353. Pierart dou Tielt, public domain.

The Black Death was not the only plague to spread along trade routes. In the sixth century, bubonic plague spread across the Mediterranean, infecting millions over two centuries. Another great outbreak of the plague started in China and India in the nineteenth century. Plague and disease have accompanied humans since we started crowding into cities and interacting with people in distant places. So how did this particular plague get to be so bad? Interestingly, it began in a period of peace.

The Pax Mongolica

The Pax Mongolica was a period from the mid-thirteenth to the mid-fourteenth century. By this time the Mongol Empire had split into four areas. Each was ruled by a “khan.” The Mongol Khans connected much of Europe and Asia’s people and enforced a general peace (“Pax” means peace in Latin). This unusually war-free time allowed more trade connections to develop all across what are now Africa, Europe and Asia, also known as Afro-Eurasia. Earlier Mongol conquests disrupted trade routes with their violence. However, the huge empire created by those conquests later connected more people than ever before under one administrative umbrella.

Map shows the extent of the Mongol empire. The land controlled by the Mongols was vast.

A map showing the extent of the Mongol Empire. Having so much land controlled by one empire made overland trade much cheaper and safer. Public domain.

Once the Mongol Khans settled down and tried to rule their vast empire, they grew increasingly concerned about tax revenue. One of the best sources of taxation came from trade. So, the Mongol Khans wanted to make trade easier and safer. For more than a century, the Mongol Empire ensured that trade networks grew and merchants prospered. The Mongols severely punished anyone who dared threaten the trade. But the flourishing of trade connections also carried the seeds of disaster.

Yersinia pestis: The Black Death

The fourteenth-century Black Death, or bubonic plague, epidemic was caused by the Yersinia pestis bacterium. These bacteria sometimes spread to humans through contact with the fluids of an infected person, but more commonly it is spread by flea bites. The bacteria get transferred to humans when fleas vomit into our bloodstreams before feeding. The effects of the bubonic plague are just as gross as how it spreads. Soon after infection, the diseased person develops swelling in their lymph nodes (called buboes). Lymph nodes are part of the immune system, and normally filter out bad substances from the body. After buboes, internal bleeding causes swellings of pus and blood to discolor the skin. It was a horrific disease that spread quickly and without warning. Most people who contracted the plague died.

A detailed image of a flea carrying the plague. There is a black, cloudy substance in the body of the flea.

A flea infected by Yersinia pestis. By the National Institute of Allergies and Infectious Diseases, public domain.

Photo of a small, furry animal standing on its hind legs. It most closely resembles a squirrel.

The Rhombomys opimus, or great gerbil. More deadly than it looks. Yuriy Danilevsky, CC BY-SA 3.0.

Merchants of death: A trade plague

Human interaction with animals and the environment also played a role in spreading the plague. For example, in Central Asia (the region west of China and south of Russia), the fleas that carried the bacteria lived on a species of rodent known as great gerbils. Just a small temperature increase, as little as 1 degree Celsius, can increase the presence of the bacteria in the gerbils by up to 50 percent. A change in climate in the middle of the fourteenth century likely helped the disease to spread out from Central Asia.

Yersinia pestis began in Central Asia’s grasslands. The disease spread through flea bites. But the fleas hitched a ride out of Central Asia on the backs of both traders and camels traveling with trade caravans. From these hosts, the fleas spread to rodents traveling with the caravans and to rats that infested trading ships. Once ships carrying plague rats and merchants arrived in other trading ports, the plague spread like wildfire. The plague likely arrived in the Mediterranean onboard Italian merchant ships. The Pax Mongolica made the Italian city-states of Venice and Genoa extremely wealthy and powerful. During this period Marco Polo of Venice traveled through the Mongol Empire. Plenty of other Italian merchants traveled east, buying luxuries in Indian ports like Calicut. The unifying rule of the Mongol Empire made these remarkably diverse interactions possible. But it also meant that, after people mingled, they brought both their cargoes of luxuries and plague- infected rats back to diverse and distant lands. Had the Mongol Empire not interconnected the world through trade and conquest, it is unlikely that the Black Death would have been so deadly or so widespread.

A map showing the spread of the plague throughout Europe. The plague started in the ports of the Mediterranean and spread inland.

A map showing the spread of the plague throughout Europe. You can see that the plague started in the ports of the Mediterranean and spread inland. By WHP, CC BY 4.0

A specter haunting Eurasia

The Black Death killed many people in the fourteenth century. As many as 100 million people across Afro-Eurasia may have died from the plague. An epidemic in the 21st century on the scale of the Black Death would kill between 1 billion and 2 billion people.

The devastation caused by the plague led to sharp declines in production and trade all over Afro-Eurasia. Even places unaffected by the epidemic suffered from disruptions to long-distance trade.

In general, the plague was the worst in Europe, which had crowded, damp, and poorly sanitized cities. The plague killed up to 25 million Europeans (out of a population of 75 million) from 1347 to 1351, one-third of Europe’s population. In some Italian cities and rural France, however, death rates approached 60 percent. Europeans tried to make sense of the death and destruction brought by the plague. Many looked around and concluded that they were witnessing the end of the world. Others began to question the authority of the Catholic Church and the social class system around them. Peasant revolts increased. In many places, angry mobs attacked Jewish communities, looking for someone to blame for their misfortune.

A dramatic painting shows unclothed humans falling and being pushed into a pit filled with demons.

The Fall of the Damned, by Dieric Bouts, 1450. Much of European art turned toward images of death after the plague. Scenes like this and representations of death became much more common. Public domain.

Death and labor: Plague reshapes European economies

Still, the horrors of Black Death were followed by some positive changes. It turns out that the sudden deaths of millions of people restructured social relationships. The transformations caused by the Black Death might have brought an end to feudalism, the social system of Europe at that time. Fewer people meant fewer peasants to work the fields of feudal lords. This gave more power to the workers who didn’t die. Soon, workers in cities and in rural areas started to demand higher wages. Wages in England, for example, rose as much as 40 percent between 1340 and 1360. The result was a higher standard of living and longer life expectancies for Europeans who survived the plague.

The rise in wages created a middle class in Europe. And with fewer workers in the fields, people were forced to get creative. Rather than rely on peasant labor, landowners started to raise more livestock. This required less labor than growing wheat. It also inspired technological innovations in farming. New plows and labor-saving devices forever changed European agriculture and encouraged other innovations. The rise of a middle class, especially in Northwest Europe, helped to revive the economy and reestablish trade networks. With higher wages, more workers could afford goods that had previously been considered luxuries. Slowly, European economies recovered, but the cultural and social changes were there to stay. The plague’s changes also likely helped to start the Renaissance in Europe.

Sources

Aberth, John. Plagues in World History. Lanham, MD: Rowman & Littlefield Publishers, 2011.

Frankopan, Peter. The Silk Roads: A New History of the World. New York: Alfred A. Knopf, 2015.

Kelly, John. The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time. New York: Harper Collins, 2005.

Routt, David. “The Economic Impact of the Black Death.” EHnet. Accessed May 6, 2019. https://eh.net/encyclopedia/the-economic-impact-of-the-black-death/

Stenseth, Nils, Noelle Samia, Hildegunn Viljugrein, et al. “Plague Dynamics are Driven by Climate Variation.” Proceedings of the National Academy of Sciences of the United States of America 103, no. 35 (2006).

Bennett Sherry

Bennett Sherry holds a PhD in History from the University of Pittsburgh and has undergraduate teaching experience in world history, human rights, and the Middle East at the University of Pittsburgh and the University of Maine at Augusta. Additionally, he is a Research Associate at Pitt’s World History Center. Bennett writes about refugees and international organizations in the twentieth century.

Image credits

Creative Commons This work is licensed under CC BY 4.0 except for the following:

Cover: Flagellants in the Netherlands town of Tournai (Doornik), 1349. Flagellants, known as the Brothers of the Cross, scourging themselves as they walk through the streets in order to free the world from the Black Death (Bubonic Plague). Chromolithograph after Chronica Aegidii Li Muisius. © Photo by Ann Ronan Pictures/Print Collector/Getty Images.

The people of Tournai (a city in present-day Belgium) bury plague victims, 1353. Pierart dou Tielt, public domain. https://commons.wikimedia.org/wiki/File:Doutielt3.jpg#/media/File:Doutielt3.jpg

A map showing the extent of the Mongol Empire. Having so much land controlled by one empire made overland trade much cheaper and safer. Public domain. https://commons.wikimedia.org/wiki/File:Mongol_dominions1.jpg#/media/File:Mongol_dominions1.jpg

A flea infected by Yersinia pestis. By the National Institute of Allergies and Infectious Diseases, public domain. https://commons.wikimedia.org/wiki/File:Flea_infected_with_yersinia_pestis.jpg#

The Rhombomys opimus, or great gerbil. More deadly than it looks. Yuriy Danilevsky, CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Rhombomys_opimus_1.jpg#/media/File:Rhombomys_opimus_1.jpg

A map showing the spread of the plague in Europe. You can see that the plague started in the ports of the Mediterranean and spread inland. By WHP, CC BY 4.0

The Fall of the Damned, by Dieric Bouts, 1450. Much of European art turned toward images of death after the plague. Scenes like this and representations of death became much more common. Public domain. https://commons.wikimedia.org/wiki/File:The_Fall_of_the_Damned.jpeg


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