The fourteenth-century plague was one of the most catastrophic pandemics in human history. In a six-month span, bubonic plague wiped out sixty percent of London’s population. Some historians estimate that it killed upwards of twenty million people within five years and by the end of the fourteenth-century, the disease—along with a famine from earlier in the century—cut Europe’s population in half. But current research proves we have some major misconceptions about the disease. I’ve combined this new information with some little-known facts, shedding light on four things most people don’t know about the Black Death.

Tartars Used the Plague as a Biological Weapon

While some researchers believe the fourteenth-century Black Death was spread via Silk Road trade, that’s not how it spread to Kaffa. We can blame a Tartar attack on the port in 1343 for that. (Tartars were Islamic converts and descendents of the Mongols living in the western part of their empire.) During the mid-fourteenth century, Tartars controlled Crimea, so when a dispute between locals and Italians in the town of Tana resulted in the death of a Muslim man, the Tartars intended to capture and kill the Italians who then escaped to Kaffa. When Kaffa refused to give up the Italians and barred the Tartars entry into the city, a sieged ensued…and lasted for three years.

A historical account written sometime between 1348 and 1349 by Gabriele de’ Mussi—a notary from north of Genoa—describes the horrific events of the third year of the siege.

… the whole army was affected by a disease which overran the Tartars and killed thousands upon thousands every day… Tartars died as soon as the signs of disease appeared on their bodies: swellings in the armpit or groin…”

“The dying Tartars… ordered corpses to be placed in catapults and lobbed into the city…. What seemed like mountains of dead were thrown into the city, and the Christians could not hide or flee or escape from them, although they dumped as many of the bodies as they could in the sea. And soon the rotting corpses tainted the air and poisoned the water supply…”

That’s right. The Tartars catapulted corpses into the city of Kaffa, turning their dead soldiers into biological weapons.

Though it seems he didn’t directly witness the siege, most consider de’Mussi’s account accurate. While some historians believed the biological warfare caused the spread of plague through Western Europe, current research suggests the two occurred independent of one another.

Most Plague Victims Weren’t Infected by Flea Bites

Most people will remember learning in school that fleas on rats transmitted the plague to victims. After a flea bite, the Yersinia pestis bacteria infected each person, symptoms ensued, and most people died. The end.

Current research proves that’s not entirely true.

When construction workers tunneling beneath London’s Charterhouse Square stumbled upon twenty-five skeletons, the long-trusted theory changed. Researchers believed the site—an unexcavated area once home to a medieval monastery—contained a Black Death cemetery. DNA extraction and analysis confirmed twelve of the victims had been exposed to and later died of the plague. Scientists compared the medieval strain of the bacteria to the strain that killed sixty people in Madagascar in 2011 and found their genetic codes were identical.

According to the World Health Organization, fleas on rats carried the Madagascar strain, but once the infection spread to the victims’ lungs, the bacteria could be transmitted via the air. This led researchers to conclude that—for the most part—coughing and sneezing transmitted the disease to medieval victims, not fleas.

To me, the air-born theory makes far more sense than the flea-bite theory, especially when considering that the disease killed sixty percent of London’s population in six months. I suppose it’s possible—perhaps even likely—that six out of ten Londoners were bitten by fleas during that six-month period, but it seems even more likely that they were exposed to a cough or sneeze. A study of wills from the time shows relatives dying within hours of one another, which I think suggests the bacteria was spread from human to human.

I suppose none of really that matters anymore since the DNA analysis and comparison with the Madagascar strain proves the plague was air born.

Fleas Might Have Been Infected By Gerbils, Not Black Rats

A new study from the University of Oslo suggests the pesky fleas who started the Great Plague were infected and transported by gerbils, not black rats. How on Earth did they figure this out? With climate data. By scouring tree ring records which coincided with 7,000 historical incidences of plague, researcher Nils Stenseth found that tree rings from Europe showed no consistent weather patterns. But, Asian tree rings did. While the wet springs and warm summers experienced in Central Asia before each outbreak weren’t suitable for black rats, they were ideal for great gerbils.

According to Stenseth in an interview with History.com, his research shows “that wherever there were good conditions for gerbils and fleas in central Asia, some years later the bacteria shows up in harbor cities in Europe and then spreads across the continent.”

And since we now know—thanks to the twenty-five skeletons found in London—that the bubonic plague bacteria has hardly changed over time, it makes sense that resurgences of plague are caused by an increase in gerbil population rather than by new strains, further supporting Stenseth’s theory.

Cat Massacres Didn’t Lead to an Increase in the Rodent Population and Plague

As I was combing the internet, I found a variety of uncited rumors about the thirteenth-century massacring of cats. Supposedly, in 1233 Pope Gregory IX issued a papal bull called “Vox in Rama.” The bull discusses the rather strange use of black cats in satanic and heretical rites. In his book, Witchcraft in the Middle Ages, Jeffrey Burton Russell describes the strange ritual.

The heretics…have secret meetings. When a postulant wishes to become a member of their congregation, he is led into the midst of the meeting, whereupon the Devil appears in the form of a toad, goose, or duck, as a black cat with erect tail which descends a statue backwards to meet his worshipers… The postulant kisses the apparition either on the mouth or on the anus.

The bull also suggests heretics participated in other rituals in which they kissed the anus of a black cat. You can read more about that here.

Despite Pope Gregory’s published opinion, I can find no evidence of people massacring cats as a result. So why is that? Probably because most people living in the 1200s wouldn’t have been aware of his opinion. It wasn’t like they could walk to the local library and pick up a copy of the bull for a nightly read. Besides, it wasn’t intended for the average person. It was intended to help bishops interrogate and root out heretics, like the Cathars.

But, for a moment, let’s ignore a lack of archeological and written evidence and say thirteenth-century people did massacre cats. The bull was issued over a century before the Black Death gripped Europe and if killing cats was a passing fancy, the feline population might have been able to bounce back by the time plague struck and kill a number of the pesky rats…or gerbils. Not that that would matter really. The plague was air born, remember?

Now this is not to say medieval people had a fondness for cats. In her article, “Heretical Cats: Animal Symbolism in Religious Discourse,” Irina Metzer discusses the general mistrust of cats during the Middle Ages. While people tolerated cats because they killed rodents, people viewed felines as “incompletely domesticated” and unwilling to serve humans when there was an expectation that God put animals on the Earth for that purpose. Primary documents show us some unfavorable conclusion about cats. People compared them to heretics, the devil, and witches.

**I want to thank my dear friend Marco for helping me with the research for this article.

Andrea Cefalo is a Medieval fiction author and history blogger. Her debut novel The Fairytale Keeper, was a quarter-finalist in Amazon’s 2013 Breakthrough Novel Contest. The sequel–The Countess’s Captive—was published earlier this year. She is currently working on the third book in her series.

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