Some time during a world history survey course in high school, or perhaps in a good documentary on the History Channel, you learned that medieval Europeans didn’t realize that rats carried fleas that carried Yersinia pestis bacteria. They were used to rat infestations and flea bites, so when they all got sick, they were puzzled and believed it was “bad air.” I’ve seen so many pictures of the rats (who scurried off ships and swam to shore, infecting the rats of each passing city) and jokes about the rats…it’s weird to find that actually rats had little to do with it.
The deadliest infectious diseases are those that jump from animals to humans; they may not be serious to the animal, and in theory, they can’t survive in a human body. But they do. Just as some common foods are actually lethal to your cat or dog, these animal infections slay millions of people. Y. pestis is an infection of rodents, but different strains live in rats or in groundhogs—or to use the formal name for the ones in Asia, marmots. Marmots are the prairie dogs of the steppes. They live all across Asia and into Northern China; their habitat is the arid grassland. And marmots, not rats, are the primary carriers of the deadliest plagues.
Much of what we think we know about Bubonic plague comes from a modern pandemic. Alexandre Yersin, a Swiss-French doctor, isolated the bacteria at the root of an epidemic in Hong Kong in 1894. This plague is known as the Third Pandemic; it began in 1855 in China. It was during this 19th century pandemic that dead rats were observed, and the linkage between fleas and Y. pestis was made. But it’s also clear that the Y. pestis strain was much weaker during the modern Third Pandemic than it had been in the past. After trying out the idea that medieval writers exaggerated, we’ve mostly settled on the realization that Bubonic plague is at its weakest if you have to be bitten by a flea. When you really worry is when it goes airborne. “Bad air” indeed.
There had been two infamous ancient plagues, the Plagues of Athens and of Justinian, and we really don’t know if they were caused by Y. pestis. We can guess, but it’s only with the 14th century one that we can know, by digging up bones to test. Most of our information about the medieval plague comes from Europe, where it shocked the population into trauma that lasted for centuries. We know a lot less about its ground zero history in China, perhaps because it was taken for granted there. We also know less about its history in the Middle East, but we know a little. Let’s look now at the plague as it affected the Mongolian domains of China, the Silk Road, and the Middle East.
The first outbreak of the bacteria from the marmot population in northern China probably came around 1330. Yuan Dynasty China had not been doing as well under Kublai’s successors, but there was also a lot of severe weather in the early 1300s. It was severe in Northern Europe, too, but both trends are generally seen as regional. As part of a larger pattern, they were early signs of massive global cooling that we call the Little Ice Age. It’s arguable that we’re only now emerging from the Little Ice Age; it’s also possible that during times of climate change, microscopic populations go through shifts that we don’t understand.
The effect was that in both northern Europe and northern China, there were terrible famines that lasted for multiple years, and more routine epidemics of things like typhoid that left the population thinned by about 10% and weakened by malnutrition. When the marmot infection crossed over, perhaps through some hunters who killed a sick animal, it met the weakened immune systems of adults who had starved as children. Between 1330 and 1350, there may have been three separate waves of plague infection in China, in various regions, each recorded at the time as slaying over half the population. Modern estimates suggest as many as 25 million deaths in the vicinity of China. We have no detailed medical descriptions from the Chinese outbreaks, perhaps because it was mistaken for other common epidemics.
We’re pretty sure that the plague came to Europe along the Silk Road. It may not have been carried by infected travelers; it may have jumped from marmots again in the steppes of Afghanistan or Iran. We don’t know. We do have signs of early plague deaths along the Silk Road as early as 1345. Over the next two years, the infections came closer to Europe and at last some Tatars who were besieging a Black Sea port began to die. Then their corpses were used as weapons, perhaps with no understanding that these corpses were much more dangerous than the usual.
The siege wasn’t very effective; ships could and did leave. Some unknown number of ships set out for Alexandria, Constantinople, and Genoa. They tried to make provision stops along the way. But somewhere between the Silk Road and the ships, the infection became airborne. And the airborne form of Y. pestis is very rapidly lethal; death can come within 8 hours of infection. This rapidity may have helped it spread slowly at first, as whole families in isolation died out without spreading it. This could be why there’s no record of the plague spreading to India, although the Silk Road ran across its northern edge. But on ships, even two hours of asymptomatic infection were enough to infect ten more people.
Within a few stops, it was clear to every harbor that the ships had plague. Probably, a boat with a few “healthy” people met to discuss the situation, and that was enough to transfer the plague ashore even if nobody was allowed to land. By the time the Genoa-bound ship had gone around the boot of Italy, everyone knew; ports shot fire arrows at the plague ships to drive them off. But it was too late.
The plague hit Alexandria, Constantinople, and port cities of Italy within the same months of 1347. It spread rapidly through Turkey and Syria, and from Alexandria, it fanned out into Egypt and North Africa. It raged through the ancient cities, devastating economies that had already been suffering from repeated conquest. Baghdad was rebuilt after its utter sacking in 1258 and was now a dirty market town: want to catch the plague there? What about depressed, crowded Constantinople or Alexandria? Damietta, anyone? Ashkelon? Oh, I know, how about Jerusalem, which had been depopulated, burned, wrecked, and repopulated in cycles for the last few centuries?
In each city, the plague stayed in a highly infectious stage for a little over a year, then new infections and deaths began to slow. About two years after the first cases, there were no new ones. So in Italy, Alexandria, and Constantinople, the hot years were 1347 to 1348, while in Germany, there were places that saw no plague cases until 1349, and it lasted into 1350.
Christian and Muslim medical science was very similar at that time, since both were based on Greek texts translated into Arabic or Latin. If you went to medical school in Pisa, you’d read works by Avicenna, a great Muslim doctor. But cultural attitudes to the epidemic were very different.
Christian societies believed the plague was punishment for sin. They tried to fight it with repentance, both with parades of relics and with flagellation to demonstrate remorse. Those who could afford to flee from the “bad air” did so, and some survived for that reason (one Italian family sealed up their house and didn’t come out for two months, while the Pope at Avignon stayed very isolated near a fire). They saw the plague as coming from God, but also as something that the saints could stop if they chose. Doctors did their best to understand the disease process, but the problem was that so many people died so fast. A man might make a last will and call in a notary to see it witnessed, only to find the notary dead, and a few hours later, his witnesses dead. When his heirs tried to bury him, they couldn’t execute the will because they began to sicken and die, and there was no time to make a proper new will. You can imagine how chaotic medical observation was, in those conditions.
The Muslim world saw the plague as a God’s will, not to be changed or fled. Death could be a merciful release from this life, and hadiths said that plague deaths were a special kind of martyrdom. Their doctors observed and treated as they could, but they may not even have been called in for most cases. While individuals might flee the epidemic, their culture did not encourage their attitudes; one hadith of Mohammed specifically says “do not flee from the plague.” Instead, their leaders encouraged greater exercise of personal piety and prayer. They probably recited the hadiths (Sahih Bukhari 622-631) about the blessed state of death from plague more often than before. On the whole, they made their wills and waited to see if they would die or live. They attended weekly public funerals for large number of the dead, instead of keeping track of individual funerals.
Lisad al-Din ibn Khatib, Vizier to the Emir of Granada, wrote a book about his plague observations. Squarely facing the hadith tradition that plague was only an expression of God’s will, he stated that so many accounts of transmission by garments, earrings, eating/drinking vessels, and direct human contact just couldn’t be ignored. He stated that the hadith tradition must be modified if it’s in such “manifest contradiction with the evidence of the perception of senses.” In 1374, about 12 years after his book was published, he was executed for heresy in Fez, possibly for his medical opinions among others.
Ibn Khaldun, whose parents died in Tunis’s plague, saw the plague as a watershed in history. Everything was going along the same each century, until the plague hit:
It swallowed up many of the good things of civilization and wiped them out. It overtook the dynasties at the time of their senility, when they had reached the limit of their duration. It lessened their power and curtailed their influence. It weakened their authority. Their situation approached the point of annihilation and dissolution. Civilization decreased with the decrease of mankind. Cities and buildings were laid waste, roads and way signs were obliterated, settlements and mansions became empty, dynasties and tribes grew weak. The entire inhabited world changed.
There’s no way to measure the devastating effect of the plague on the cities left behind. Whole houses were left empty, whole professions stripped of masters and teachers. In England, the routine teaching of French at school came to an end. Some large buildings lost their architects and had to be completed in simpler ways. So many priests died in Europe that the old apprenticeship training system fell apart; they had to found seminaries to train young men in larger groups. There were chaotic population transfers between farms and towns, as vacancies got filled. Within two generations and about four plague episodes, Europe’s feudal system was mostly dead and peasants began uprisings to demand wages.
Constantinople was gutted. The plague was the last blow to this city that was once the capital of its region, with the best of everything. After the Fourth Crusade burned much of it, and then the Byzantines spent 50 years battling back into power, there was much to recover from. In 1347, the recovery shut down. There’s a direct link between the plague and the city’s humiliation in having to pay tribute to the Turks around 1360. By 1371, when peasant revolutions began to roil Europe, Constantinople was officially a vassal state.
The last Ilkhan descended from Hulegu died of plague during early Silk Road outbreaks in the 1330s. His heirs all died with him, leaving a complete vacancy, which led to the break-up of the Ilkhanate into warring, impoverished cities. The new Mamluk Sultan, a 12 year old boy, survived but the city was weakened, which must have affected Mamluk politics.