What Caused the Great Mortality in 14th Century England?


By Dorsey Armstrong, Ph.D., Purdue University

As far as years in history go, 1348 was not a very good one, especially in Western Europe. The bubonic plague was ravaging the medieval world. The people who lived through it called it the Great Mortality, or the Great Pestilence, or sometimes Blue Sickness. It was only in later centuries that the term Black Death would be coined.

Image of a barefoot corpse wrapped in blanket and left in the autumn forest
In a population that was already weakened by the occasional famine and poor health due to scarcity of arable land, this disease had a devastating impact. (Image: Jan H Andersen/Shutterstock)

High Death Toll in England

While the three forms of plague, later called the Great Mortality, caused by infection with the bacterium Yersinia Pestis were certainly the major dealers of death here, many scholars wonder if other epidemics were raging simultaneously, contributing to the high death toll. This certainly appears to be the case in England.

Contemporary accounts from England describe several instances of the telltale buboes appearing in the groin and armpits of infected individuals, but there are also rather shocking tallies of dead animals and specific references to a murrain that wiped out huge herds of livestock. 

Image of an old cemetery at dusk.
The three forms of plague caused by infection with the bacterium Yersinia Pestis were the causes of many deaths in England. (Image: Javier Garcia/Shutterstock)

We know that the plague affected both human and animal populations in Florence, but in England, the accounts are rather extreme, which leads some to wonder if there might have been some other agent at play—maybe anthrax, which can naturally occur in the environment, or some other disease that we haven’t yet identified that went zoonotic, meaning it jumped from the animal to the human population. 

Or maybe there was some kind of viral, hemorrhagic fever that we haven’t yet identified which was sweeping through the medieval world at the same time as the plague—maybe something like Ebola, or maybe even a virus like HIV. In a population that was already weakened by the occasional famine and poor health due to scarcity of arable land, such a disease would have had a considerable impact.

Learn more about the Black Death’s ports of entry.

Great Mortality: Ingredients for Perfect Storm

What we do know is that prior to the arrival of the Black Death in England, there was a perfect storm of circumstances that made that region both an ideal incubator for disease in the physical sense, and in a social and economic sense. Changes in the daily life and infrastructure in the first half of the 14th century meant that the impact of the disease would be much more severe. 

When looking at chronicle accounts of the arrival of the Black Death in England, one is struck again and again by how many people start out by talking about the weather. There is a recurring pattern in their accounts of how there was so much rain pouring down on them.

Image of rain ruining crops.
With so much rain, the harvest was poor, and many crops started to mold and rot in the ground. (Image: Matauw/Shutterstock)

The writers of these documents saw a connection between the two. Now, to the medieval mind, this may very well have been something like: “Things were miserable for six months, and then they got more miserable with this disease, and so clearly it seems that God was mad at us.” But to the modern mind, and to scholars who study this event, it seems more likely that the bad weather created a situation in which the plague was perfectly poised to effect maximum damage.

With so much rain, the harvest was poor, and, many crops started to mold and rot in the ground if they weren’t washed away entirely, this meant that nutritional instability, which was already present in an English population that had doubled in the space of a couple of hundred years, was suddenly that much worse.

This is a transcript from the video series The Black Death: The World’s Most Devastating Plague. Watch it now, on Wondrium.

No More Crops for You

In the years before the arrival of the Black Death in England, there are accounts of people grinding up tree bark and mixing it into their grain in order to produce bread with a bit more heft in order to fill their bellies. 

People of course still had to eat, but the wheat and other crops may have been infected by mold, which could have contributed to outbreaks of illness. This situation might also explain why there was such a huge die-off of sheep and cattle.

The unusual weather perhaps created a situation in which certain infectious diseases were made into superbugs. Or, as some have theorized, it may have somehow exposed people and livestock to new viruses with which they had not come in contact before. 

Learn more about the medieval theories about the Black Death.

The Stage Was Set for the Great Mortality 

It’s well known that livestock diseases like liver fluke and rinderpest flourish in damp weather, so these may be at least two of the culprits here. But science, to this day, is continually making discoveries about new viruses and bacteria. And science is also discovering bacteria and viruses that have been around all along but that we humans have not recognized before—and it’s possible that the strange weather had unleashed something into the livestock population that was a novel disease. 

We also know that there had been an earthquake reported near York in late 1348, a natural disaster that may have displaced some rodent populations who were carriers of disease and not just plague, but other diseases as well.

So, in a nutshell, the food situation was bad. Most of the population was already weakened by this fact, and in the first half of the 14th century, a land crunch had made the agrarian life of subsistence farming no longer a possibility for many people.

Common Questions about What Caused the Great Mortality in 14th Century England

Q: What could have been the cause of the high death toll in England in the 14th century?

Besides the Black Plague ravaging England, the circumstances for the Great Mortality were just right. The weather was damp enough for the easier spread of disease, with crops and livestock also affected. 

Q: What were the negative effects of bad weather in England before the Black Plague?

The weather made an unusual environment for the spread of what you could call ‘super diseases’. The huge amounts of rain also meant the crops were washed away or if they weren’t, they would rot in the ground. This set the scene for the Great Mortality that was yet to come.

Q: What would people in 14th century England have thought about the bad weather before the spread of the Black Plague?

Before the Great Morality, the people would have seen a cause-and-effect relationship between these two phenomena. But maybe differently than us. They would perhaps have thought about how God was trying to punish them for something.

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Black Death and its Impact: The Catastrophe that Ravaged Europe
The Impact of Plague: The Plague of Justinian and the Black Death