The Black Death and Justinian’s Plague: History’s Worst Pestilences

16. A Plague’s Journey From China to Europe

Modern research and scholarship has pinned the Black Death on Yersinia pestis, a bacterium with no spores. Per genetic analysis, a strain of Yersinia pestis caused that plague. However, it did not die off at the end of that pestilence. Instead, it has lingered around ever since, mutating and reappearing from time to time to cause additional plague outbreaks. The most recent major outbreak, known as the Modern Plague or the Third Pandemic, emerged in China in the mid nineteenth century. It was carried by rats aboard steamships all over the world, and killed an estimated 10 million people. As to the original, the Black Death first erupted in Mongol-ruled China and Central Asia in the 1330s. It traveled the Silk Road with merchants and Mongol armies, and took about fifteen years to reach Europe in 1347.

15. The Long History of the Black Death’s Origins

The Black Death first erupted in China. However, its bacteria might have originated in Europe thousands of years before. Evidence of Yersinia pestis was found in a Swedish tomb that dates back to circa 3000 BC. It could have caused a devastating plague thousands of years ago that led to the Neolithic Decline, when Europe’s population crashed. It also caused Justinian’s Plague, a sixth century pandemic that, as seen further below, rivaled the Black Death in deadliness and devastation. The Black Death first reached Europe through a 1346 siege when the Mongols set out to capture the city of Caffa, now Feodosiya, in the Crimea. In an era of poor sanitation and medical knowledge, sieges were often as deadly for the besiegers as the besieged, because the besieging armies encamped around the targeted city often came down with various diseases.

14. Catapulting Infected Corpses

When the Black Death struck the Mongol besiegers of Caffa, their commander, Jani Beg, decided to share the misery. So he catapulted corpses of plague victims over the walls into Caffa, to infect the inhabitants. Some Genoese traders in the city fled, and carried the plague with them to Mediterranean ports. They arrived in Sicily in 1347, which they infected, and from there, the Black Death spread north to the Italian mainland and thence rapidly to the rest of Europe. When the plague hit Europe and the Mediterranean, it spread as rapidly as, well as… well… the plague. The Genoese traders who had carried the pestilence with them when they fled from Caffa stopped in Constantinople along the way, and gifted it and the rump Byzantine Empire with the plague before they continued on to Sicily.

13. The Rapid Spread of a Deadly Plague

From Sicily in 1347, the Black Death swiftly reached the islands of Sardinia and Corsica, plus Naples in Italy, that same year. The next year, it spread to the rest of mainland Italy, France, two thirds of the Iberian Peninsula, southern England, the Balkans, Egypt, Anatolia, and the Eastern Mediterranean in general. In 1349, the plague reached Germany and Central Europe, most of Ireland, plus the rest of England, the Middle East, and North Africa. In 1350, Scotland, Scandinavia, and the Baltic shores were hit. By 1351, the Black Death had ravaged most of Europe, except for relatively unaffected pockets in Poland, plus the western parts of Belorussia and Ukraine.

12. A Horrible Way to Go

By all accounts, the Black Death was a terrible way to go. It was especially horrific in its most common form, the Bubonic Plague, named after the buboes, or swellings, that marked its victims. Painful swellings, or buboes, first appeared in the groin and armpits, where fleas infested with the plague gravitated. The first swellings usually occurred near the site of the initial infection, caused by the flea’s bite, or by the victim’s scratching of the bite site. From there, the buboes spread to the rest of the body. Next came a high fever, accompanied by bouts of vomiting blood. Muscle cramps, chills, skin decomposition, and severe seizures, were also among the plague’s symptoms. The victims tossed and turned in the throes of agonized delirium as they burned up with a steadily worsening fever.

11. Black Death Varieties

If a Black Death victim lasted for more than a few days, he or she might get to experience the final ravages of the plague: gangrene that ate away at the extremities and blackened fingers, toes, lips, and nose tip. Few lasted more than a few days, and many died within half a day of the first symptoms’ appearance. The bubonic plague was the most common form of the Black Death. However, the plague had two other deadly strains: the septicemic and pneumonic plagues. The differences were in the affected body parts. The bubonic plague hit the lymph nodes, the pneumonic targeted the lungs, while the septicemic infected the blood.

10. Septicemic vs Pneumonic Plague

The septicemic plague was a blood infection that clotted the veins. Victims suffered from abdominal pains, bled under the skin, had blood pour out of all orifices, vomited of blood, and experienced fever, shortness of breath, and gangrene. The pneumonic plague struck the lungs, and caused symptoms such as chest pains, shortness of breath, coughs, headaches, and high fevers. It could follow an initial bubonic or septicemic plague infection, and strike those lucky enough to have survived one of the other plague strains, only for their luck to run out when they came down with the pneumonic plague. It could also be contracted from airborne particles exhaled by infected humans or cats.

9. The Black Death Went Away for a While, but Kept Coming Back for Decades

By 1352, the Black Death had mostly burned itself out. Mostly, but not completely. Like a persistent ex turned crazy stalker, the Yersinia pestis bacterium continued to return to wreak more havoc in subsequent decades. There were further outbreaks in 1361 to 1363, 1369 to 1371, 1374 to 1375, 1390, and 1400. None of the recurrences were as horrific as the original mid-century one, but they were still pretty bad: each time they hit, they killed about 10% to 20% of the population. All in all, in the second half of the fourteenth century, the plague was introduced and reintroduced to Europe numerous times, arriving along the trade routes from China and Central Asia in multiple waves. Modern research suggests that climate fluctuations played a key role in those recurrences, as they affected populations of rats and other rodents infested with the plague-carrying fleas.

8. Weather and the Plague

Fourteenth century weather fluctuations played a key role in the Black Death’s recurrences. The plague bacterium, Yersinia pestis, thrives on fleas that are usually hosted by ground rodents such as marmots – which don’t mingle with humans. However, bouts of bad weather in the 1300s struck those rodents’ habitats and decimated their populations. So their plague-infected fleas fled to alternate hosts such as rats – which do thrive amidst human populations. As seen below, a plague cycle developed, driven by weather fluctuations.

7. The Black Death and Weather Cycles

Bad weather kills off the usual rodents – which don’t live amongst humans – that host the fleas that host Yersinia pestis. The fleas then flee to rodents like rats that do live among humans. A Black Death outbreak starts. Even as they kill humans, the infected fleas also wipe out their rat hosts, and thus extinguish the plague. Ten or fifteen years later, bad weather would again decimate the usual rodents that typically host the infected fleas. Once again, the fleas flee to rats, whose populations by then have recovered. The rats reintroduce the plague-infected fleas to humans, and another Black Death outbreak occurs, that lasts until the rats die off.

6. A Great Shock

The shock of a plague that wiped out up to two thirds of the population was great, to say the least. Take the experience of the world’s reaction to the recent Covid-19 pandemic, and multiply it many times over, to get an idea of how contemporaries felt about and reacted to the Black Death. The economy contracted sharply, as trade came to a standstill, and wars came to a halt. However, astonishing as it might seem to us today, medieval people soon adjusted to the Black Death, grew accustomed to the plague, and took its frequent recurrences in stride.

5. The Consequences of the Plague

The immediate reactions to the first and deadliest Black Death wave were only temporary: the dead died, but life went on for the survivors. Within a few years, trade resumed, the economy picked up, and the survivors went back to waging wars and settling their disputes and differences by killing each other. The Black Death’s longer term consequences revolved around the sudden impact of a significantly reduced population. In many parts of Europe, the land under cultivation shrank because many serfs and laborers had died. However, that often led to an increase in productivity in the land that was still cultivated. With more land available than could be cultivated, people focused on the best agricultural lands, and abandoned more marginal lands or turned them into pastures.

4. A Plague That Changed the World

The shortage of labor was also a boon to surviving laborers. Faced with a labor scarcity, landowners and employers were forced to compete for workers by offering them better wages and working conditions. Those changes brought new fluidity to a hitherto rigidly stratified society. The land economy survived, but was weakened, as a new money economy – which ultimately replaced it – emerged.  Psychologically, the shock of the Black Death caused more people to ask more questions to which the Catholic Church had few answers. That served to speed up and fuel the budding Renaissance. The world would never be the same.

3. A Plague That Might Have Been as Bad as the Black Death

The Black Death was history’s deadliest plague, but Justinian’s Plague, 541 – 542 AD, gives it a run for its money in lethality and consequences. It was named after Byzantine Emperor Justinian I, in whose reign it occurred – and who came down with it, but survived. It is history’s first known recorded pandemic, because it swept across three continents, Europe, Asia, and Africa. Like the Black Death, Justinian’s Plague was caused by the Yersinia pestis bacterium. Also like the Black Death, Justinian’s Plague struck with a devastating initial outbreak, followed by several recurrences in subsequent years. By the time the last recurrence ended and Justinian’s Plague died out, it had killed an estimated 25 million to 100 million people.

2. The Origins of Justinian’s Plague

The Yersinia pestis strain responsible for Justinian’s Plague probably originated near the Tian Shan Mountains, between China and Kyrgyzstan. Like the Black Death, Justinian’s Plague was mainly bubonic, and felled its victims with all the bubonic plague’s horrors. The pandemic is believed to have first struck China and northern India, made its way via trade routes to the Great Lakes region of Africa, then down the Nile to Egypt. Like the Black Death, Justinian’s Plague was transmitted by infected fleas carried by black rats. Egypt was the Byzantine Empire’s granary, and from its seaports, ships laden with grain – and also rats hosting infected fleas – sailed across the Mediterranean. From Egypt, the plague rapidly spread to the rest of the Middle East, the Eastern Mediterranean, and Constantinople, which served as both capitol and commercial center for the Byzantine Empire. From Constantinople, the pandemic rapidly spread through the rest of Europe.

1.     Like the Black Death, Justinian’s Plague Reshaped the World

Justinian’s Plague hit Europe hard. The continent lost 40% to 50% of its population. However, the pandemic followed the established trade routes, so ports and cities were hit the hardest. The countryside and the parts of Europe off the established trade routes got off relatively lightly. That lopsided death toll, heavy in the cities and relatively light in the countryside, marked a transitional point for Europe. It ended what was left of the Classical Age, and ushered in the Feudal Era. The Classical Age had been marked by a significant urban culture. Justinian’s Plague – on top of Justinian’s many wars – put paid to that, as it devastated the cities and an economy built around sustaining urban life. The center of power shifted from urban centers to the countryside, and rural strong men emerged as the founders of feudalism. One era and way of life ended, and another one began.

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Where Did We Find This Stuff? Some Sources and Further Reading

Cantor, Norman F. – In the Wake of the Plague: The Black Death and the World it Made (2001)

Centers for Disease Control and Prevention, CDC – How Plague Spreads

Crawford, Dorothy – Deadly Companions: How Microbes Shaped Our History (2018)

Encyclopedia Britannica – Black Death

History Collection – Mad Myths in History That Just Won’t Go Away

Listverse – 10 Scary Facts About the Justinian Plague

McNeil, William H. – Plagues and People (1976)

Medievalists Net – Yersinia Pestis and the Plague of Justinian 541-543 AD: A Genomic Analysis

World History Encyclopedia – Justinian’s Plague (541-542 CE)