“I have been urged to write what happened here. Every city, every settlement, every place was poisoned by the contagious pestilence. When one person had contracted the illness he poisoned his whole family, and those preparing to bury the dead were ceased by death in the same way. thus, death entered through the windows, and the cities and towns were devastated, and survivors mourned their dead kin.”Gabriel de Mussis
“Such terror was struck into the hearts of men and women by this calamity that brother abandoned brother and the uncle his nephew and the sister her brother and very often the wife her husband. But what was even worse and quite incredible was that fathers and mothers refused to see and tend their sick children as if they had not been theirs.”Giovanni Boccaccio
“I, brother John Clyn of the Friars Minor of Kilkenny, have written in this book of the notable events which befell in my time, so that such deeds should not perish in time or be lost from the memory of future generations. I leave parchment for continuing the work. In case anyone should be alive in the future, and any Son of Adam can escape this pestilence and continue the work thus begun.”John Clyn, Friar and chronicler.
Reaching the seaport city state of Florence in early 1348 the great mortality or great pestilence, as contemporaries referred to the calamity that had befallen them, carried off half of Europe’s population within three short years. Once the disease had conquered the densely populated towns of Italy and subsequently France, it continued its crusade with great speed and efficiency. By moving anti-clockwise through the lands, it put a deadly noose around the region from which there was no escape.
Christian, agricultural and feudal, with opportunities for social advancement very limited, Europe was nevertheless no place caught in a dark age. On the contrary, prior to the arrival of the plague, the economy was thriving. Commercial powerhouses, namely the Italian city states, allowed a rising merchant class to flourish. Market towns all over the continent were bustling with activity, and it was here that all social classes mingled. Tradesmen, clergy and the nobility were constantly on the road, and, because of the merchants advancing their business interests steadily, society was already poised to change. Massive population growth, caused by the little climatic optimum as well as new advances in farming techniques, had started to shake up the ‘three estates’ constituting medieval societies. This process, most scholars believe, was hastened by the Black Death. Indeed, the world in 1360 had very little in common with that in 1340. As communities teetered on the verge of anarchy, it was hardly surprising that the pestilence, at least initially, brought out the worst in men. Insanity, best embodied by the Flagellants, and scapegoating were present almost everywhere, leading to the worst anti Jewish pogroms predating the holocaust. With the ruling classes often heavily indebted to Jewish moneylenders, these pogroms were largely elite driven, giving the upper classes a chance to liquidate their creditors. But the survivors of the disease embraced a new world. Especially for peasants and labourers, the aftermath of the Black Death presented new and unheard-of opportunities, with serfdom and feudal certainties gradually withering away. While the English monarch, King Edward III was quick to react and did his best to preserve the status quo by introducing the Statute of Labourers in 1351, the ‘lower orders’ had already moved on, and, like elsewhere, his attempts were doomed to fail.
History and epidemiology
Each generation that lives through a pandemic believes the experience to be unique. However, nothing could be further from the truth. Roughly speaking, the pestilence hit with great ferocity in three epidemic waves, with the Plague of Justinian (541 549 AD) having been the first. Named after the Byzantine emperor Justinian I who, according to author and historian Procopius, contracted bubonic plague himself but miraculously recovered, the disease killed 20% of Constantinople’s residents and between 30% to 50% of the people living in the empire and beyond. Like the Black Death 800 years later, the economic and political consequences were enormous. During his long reign, Justinian I was desperate to restore the by then already defunct Western Roman Empire, and some scholars argue today that his attempts were hampered by the plague epidemic, since it put severe strain on both the military and burocracy. Besides, both major epidemics led to new cultural sensitivities. As devastating and catastrophic as these outbreaks were, they sharpened the pen of great writers. It was the life altering experience of multiple generations which, in the mid14th century, allowed authors like Giovanni Boccaccio, William Langland and Geoffrey Chaucer to step forward, producing some of the finest literature to date.
Once the second epidemic had started to ebb in the early 1350s, plague would remain a constant recurrence throughout the Middle Ages, even though outbreaks were largely confined to specific regions and less virulent. Overall population growth was slow, and numbers didn’t recover until the early 17th century. Sometimes, the onslaught of the Black Death still wrought havoc in society and are well remembered even today. A prime example for such a major outbreak was London in 1665. Unknown to contemporaries at the time, the pestilence was finally about to loosen its terrifying grip on communities and in Europe eventually disappeared completely. But there was little respite for the population, as other infectious diseases, such as Smallpox, Syphilis and Tuberculosis quickly filled the void.
It was not until the third epidemic devastated Asia during the second half of the 19th century that the cause for the disease was established. Equipped with germ theory, the bacterium Yersinia pestis was discovered in 1894 by two scientists almost simultaneously. Despite Japanese physician Shibasaburo Kitasato publishing his findings ahead of his Swiss counterpart Alexandre Yersin, the more detailed and thorough description of the bacterium led to Yersin being credited with its discovery. Now that the pathogen causing plague had been isolated, detailed research into the epidemiology of the illness could begin. Just a few years later in 1898, Paul-Louis Simond showed comprehensively the rat flea to be the vector for transmission. The plague comes in three distinct forms: Bubonic, Pneumonic or Septicemic. Already back in the mid1400s, Guy de Chauliac, physician at the papal court in Avignon, distinguished between two different forms of the disease, one form causing the bubos and another affecting the lungs. With modern medicine and antibiotics at our disposal bubonic plague, the most common form of the disease, is easily treatable if diagnosed early. However, once the bacteria migrate from the lymphatic into the respiratory system and cause pneumonic plague, victims literally drown in their own blood. While rare, the septicemic form is the most difficult for us non-physicians to comprehend. Nevertheless, let’s give it a try. Once the bacteria enter the bloodstream, it causes something known as disseminated intravascular coagulation which leads to the blood clotting. Tiny blood clots in turn result in something called localised ischemic necrosis which describes the process of body tissue dying off. Even today, pneumonic and septicemic forms of the disease are almost always deadly. According to the World Health Organisation (WHO), approximately 2000 cases are being reported each year, with most of them originating in Madagascar, the Democratic Republic of Congo and Peru. Yet, the disease puts in a regular appearance in the ‘developed world’ as well. For example, in the southwestern parts of the US, 1-17 people catch the illness each year, and in 2015 it claimed the lives of 4 people.
Until very recently, modern medicine grappled with what the Black Death actually really was. Especially its rapid spread led some historians and biologists to call into question the conventional theory that the illness was caused by Yersinia pestis and introduced into the human population by rat fleas. The late David Herlihy, who was a US historian and an authority on medieval societies, questioned the conventional wisdom on the subject. In his book The Black Death and the Transformation of the West, he contended that, because there had been no reports of any episodic event preceding the second epidemic, the high mortality rates could not have been due to plague alone. But Herlihy’s beef with conventional scholarship didn’t end there. The relentless advance of the disease cannot be explained by maintaining that the illness travelled along international trade routes. He raised another intriguing question. Plague moves in seasonal cycles, being at its worst in summer before receding in winter and then resurfacing once the weather turns warm again. Epidemiologically, however, the most conducive time for transmission from rodents to humans would have been in the winter, as most people were indoors, and rats and humans lived in close proximity to each other. However, as we know, this is not what happened.. Biologist Graham Twigg made out another possible culprit: Anthrax poisoning. In his volume The Black Death: A Biological Reappraisal published in 1984, Twigg argued that bubonic plague is a much misunderstood disease, and that most medieval epidemics were caused by Anthrax. Like Yersinia pestis, Anthrax is a bacillus that can easily jump from animals to humans, and one of the most common forms of exposure was eating cattle meat. At the time, fatality rates were between 80% and 85%, and symptoms were similar to plague victims. While the mortality rate has been greatly reduced, even today, 40% to 45% of cases, as rare as they might be these days, end in death. In his writings, historian Norman Cantor argued along similar lines, suggesting that 20% of fatalities during the Black Death may have been due to Anthrax. Relying heavily on something called Cometary Panspermia, astrophysicists Fred Hoyle and Nalin Chandra Wickramasinghe made some of the most outlandish claims regarding the origins of plague. In their coauthored book Diseases from Ouuter Space – Our Cosmic Destiny, they posited that the pestilence came from space.
“To argue that stricken rats set out on a safari that took them in six months not merely from southern to northern France but even across the Alpine massif borders on the ridiculous. What remarkable rats they were, to have crossed the sea and to have marched into remote English villages, and yet to have effectively bypassed the cities of Milan, Liege, and Nuremberg. There was no marching army of plague-stricken rats. The rats died in the places where they were.”Diseases from Outer Space – Our Cosmic Destiny, Fred Hoyle & Nalin Chandra Wickramasinghe.
Leaving aside the character and wanderlust of mid14th century rats, the idea that plague dropped from the heavens above on an unsuspecting devout population is to say the least far fetched. Since vertical transmission is difficult to prove, the authors contentions enjoy only fringe support among scholars. If nothing else, reading their book makes for some lighthearted entertainment. In 2010 a famed study, headed up by anthropologist Barbara Bramanti, settled the issue beyond any reasonable doubt by identifying Yersinia pestis Medievalis as the main agent of the Black Death. How virulent this particular strain of the bacillus is was on display during a major outbreak in Madagascar in 2014. Recent scholarship, exemplified by a team of researchers from the University of Oslo, has started to focus attention on a possible correlation between non-anthropogenic climate change and plague outbreaks. Indeed, in his groundbreaking study The Great Transition: Climate, Disease and Society in the Late Medieval World, Professor Bruce Campbell put forward a compelling case for climate change strongly having impacted upon medieval societies. Changes in atmospheric circulation, helped along by the eruption of the Samalas volcano in 1257, cooling global temperatures by about 2 degrees, led to huge fluctuations in weather patterns and in consequence to enormous environmental stress. While not a monocausal relationship, most scholars nowadays agree that environmental changes influence but do not determine societal outcomes. To what extent climate instability facilitated the outbreak and spread of the Black Death is a question presently studied very closely by modern science.
The plague village Eyam: A case study in genetics and immunity
In September 1665, the village tailor received a parcel containing flea infested cloth from London. How was this poor man supposed to know that by opening the package, he would invite death right into the heart of his community. The struggle for survival that followed has been memorialised by Pulitzer Prize-winning author Geraldine Brooks. In her novel Year of Wonders, she tells the story of a community going into quarantine voluntarily rather than to flee and spread the infection further. Eyam seemed doomed – but was it? When outsiders entered the village one year after the plague had struck, they noticed to their astonishment that only half of the population lay dead. What happened in Eyam did not just appeal to the sensibilities of a great author, but also engaged the rational inquisitive minds of scientists.
„I think all scientists like to make new discoveries and like to learn new things, but I think the ones who really make the most critical advances are the ones who cannot stand not to understand what happened.” Motivated initially by his research on the HIV/AIDS pandemic, and heartened by the discovery of the genetic deletion mutation CCR5 delta32 which gives partial and in the case of homozygous full immunity against HIV/AIDS, US geneticist Stephen O’Brien wanted to solve another related mystery. At what stage did the mutation confer a selective advantage to those carrying it when reproducing? In other words, when did the delta32 mutation become statistically relevant in our gene pool? Even though plague is caused by a bacterium and HIV/AIDS is a viral infection, both diseases hijack the human immune system in similar ways. For O’Brien therefore, plague was the most likely candidate warranting further investigation. In order to test his hypothesis that delta32 afforded those carrying it protection from the Black Death, O’Brien had to first find a plague-stricken isolated place. Eyam folk are proud of their heritage, and even today many of its residents can trace back their family trees to medieval times. Thus, O’Brien had found the place he had been looking for. “The Eyam population is a fascinating opportunity to look at really what is a natural history experiment to understand the interaction between plague and genetic resistance. Virtually everybody was exposed to the plague bacillus, and a very high fraction of them died as a consequence. The few survivors that emerged afterwards intermarried and left a legacy if you will of descendants, and by looking at their genes we are wondering whether we can discover that gene that caused resistance to that plague.” Analysing DNA samples taken from those with proven medieval ancestry, the results showed the presence of delta32 in 14% of the population and 4% carrying two copies of the mutation. According to O’Brien, this was a significant number. Sensing that he was onto something big, O’Brien put together an international team of scientists to map the frequency of the mutation worldwide, and what he found was indeed remarkable. “So we began to look more carefully across people of different populations and ethnic groups in Europe, Asia, Africa and Southeast Asia, and we discovered that the gene frequency was not the same in every place.” According to O’Brien, delta32 is only present in Europe and the United States and there only among those with European ancestry. More stunningly, the frequency of delta32 precisely matched the path the Black Death had taken in the mid14th century. But would it be possible to establish when delta32 emerged significantly in the population? To do this, scientists had to develop a complex mathematical formula to determine at what time the mutation dramatically increased. They concluded that this happened 700 years ago as the Black Death wrought havoc in Europe. Geneticists assume that 10% of Europeans carry one copy of delta32 which can delay the progress of AIDS but does not prevent infection. However, homozygous, making up 1% of the total population, seem to be immune against the HIV virus.
Here is something for grownups to consider. As intriguing as these findings may be, they must not be used to encourage artificial meddling with our genes. We possess them for a reason, and mutations are in most cases detrimental to those carrying them. Some researchers have recently suggested that delta32 might be associated with premature mortality, even though they conceded that their study was only preliminary and additional research is needed. Delivering the5th Darwin lecture in Cambridge in 2014, O’Brien warned that delta32 has its drawbacks. “So yes, delta32 is a risk factor, a huge risk factor. Most of the people who die of West Nile Virus are delta32 homozygous.” Put differently, delta32 is a blessing and a curse.
The present: Infectious diseases as a lingering threat
“Sensationalising the plague does not help us to deal with the reality of pandemics, but neither does the lack of attention given to plague in areas of the world that are often beneath our notice.”The Black Death and the Future of the plague, Michelle Ziegler.
And what about the pandemic we are all currently living through? Day in day out, we are exposed to wall-to-wall coverage of the Corona virus. Around the clock, journalists and pundits appear on television, in print or on social media to tell us what Corona is, and how it is going to effect our societies for years to come. Many among them heed their self-righteous calling with such zest that they resemble more and more a bunch of headmasters preaching to a group of students who in their view are a bit slow on the uptake. Granted, Corona is real and serious, but is it disastrous? Adding a historic perspective can help avoid the hyperbole surrounding much of the reporting on the subject. More is to be gained by at least occasionally reminding ourselves what Corona is not. It is not the plague – in fact, it is not even the Spanish Flu which in 1918/19 killed between 50 to 100 million people globally or 3% to 5% of the earth’s entire population, cutting down many in the prime of life. For COVID-19 to become anything like the Great Influenza, the virus would have to claim the lives of 200 to 400 million people. Does this come across as an academic exercise in cold-blooded detached number-crunching? Perhaps, but please remember that the mortality rate is the most reliable indicator as to the severity of a pandemic. Not withstanding grave personal tragedies and collective hardship, except for inflated budget deficits and an economy temporarily on a nosedive, this virus will not threaten the social fabric of our societies. The much more serious threats to our survival on this planet persist, however, namely climate change and environmental decay. Alas, history poses another question. If the bouncing back of medieval Europe testifies to the resilience of the human spirit, I cannot help but wonder how our ‘modern’ societies would fare if, god forbid, a similar catastrophe were to occur. Would the survivors of such an event recover as quickly as our ancestors in the Middle Ages did? Well, I must leave this for the reader to ponder.