The following are the first 2 chapters from the book “The Black Death – Explore the Great Mortality From Beginning to End “

What’s in A Plague?

The word “plague” and its cognates or equivalents in other languages have had many uses and connotations throughout the centuries. The word comes from a very old Indo-European word found in many languages. The Latin and Ancient Greek forms of the modern word are from plāga and plēgḗ, respectively. They both mean a blow or wound, such as one caused by a sword. Over time, this meaning was expanded to include any event that left people worse off or unwell, not just wounded. To be plagued meant to be harmed in some way, and to plague someone or something was to harm it. Bandits can “plague” a countryside, or a family or a house can have a “plague” of disasters upon it.

The metaphor easily extended to mean an event where a disease strikes an area. Over time, the word grew closely associated with illness epidemics or pandemics, until finally, “plague” became synonymous with a disease in the ancient world. It was a generic term that did not have an association with a specific disease, however. This, coupled with the lack of medical knowledge in the ancient and medieval world compared to modern times, means that determining exactly which disease a historic “plague” was can be challenging.

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Even with modern medical knowledge and DNA analysis, getting a clear picture of past pandemics is challenging.

The period of crises and pandemics in Afro-Eurasian history known as the Black Death is particularly troubling in that regard. In Europe and elsewhere, there was a wealth of information recorded about the disease(s) and the people who struggled to survive. Graphic, frightening details about emptied countrysides and hellish cityscapes choked with bodies are readily available in almost every country in Europe. These cultural memories have influenced the way Europeans think about their history, as much as the plague influenced history itself. Yet those accounts don’t lead us to a single all-encompassing answer as to what the Black Death was, how it spread, or how many people it killed.

It is important to make a note of that fact, and keep it in mind going forward. There are strong and very well-researched theories that have been put forward over the years, without a doubt, and some are so widely regarded by the scientific community that the public often treats them as fact. The debate is also as healthy as ever today, ensuring that new technology and discoveries help to push the envelope on what we know about this most infamous of pandemics.

Though there might always be a degree of mystery and enigma surrounding the Black Death.

Yersinia Pestis & Friends

The most commonly accepted theory for the Black Death is that it was caused by a bacterium named Yersinia pestis.

  1. pestis was independently identified by Japanese bacteriologist Kitasato Shibasaburo and Franco-Swiss doctor Alexandre Yersin in 1894. Though they discovered it practically simultaneously, Yersin was credited with linking the bacterium to the plague first and received the dubious honor of having the microscopic killer named after him. The bacterium comes in many subspecies, which can cause a variety of diseases collectively known as plague, each with different symptoms and means of infection. The three main forms of plague are pneumonic, septicemic, and the most famous, bubonic.

Pneumonic plague is a lung infection that may follow an infection by septicemic or bubonic plague, or it can occur by itself after inhaling airborne droplets infected by the bacterium. Its symptoms are a severe cough, shortness of breath, fever, chest pain, or headaches. This made pneumonic plague indistinguishable from dozens of other respiratory diseases with similar symptoms in the pre-modern world before effective medical testing existed.

Pneumonic plague is rarer in the world than bubonic plague, but also more deadly. While the majority of bubonic victims will survive the infection, pneumonic plague was more commonly fatal than not, prior to the development of modern medicine. Because it can spread through the air without physical contact with a human or animal host, it also spreads much faster than bubonic or septicemic plague when it does flare up.

Septicemic plague is the deadliest form of plague. It is a blood infection normally transmitted by the bite of infected fleas and other pests, including some mammals. It can also spread when infected material touches an open wound, or more rarely by breathing in bacterium droplets like the pneumonic plague. Symptoms include fever, chills, low blood pressure, bleeding from orifices or under the skin, nausea or abdominal pain, vomiting blood, necrosis in the extremities, and eventual organ failure leading to shock and death.

Septicemic plague is, fortunately, the rarest form of plague with a very slow rate of infection. This is partly due to how deadly it is—host death can occur extremely quickly before it even has a chance to spread further. Sometimes, death occurs before outwardly visible symptoms appear, making the disease extremely difficult to identify before modern testing existed. People seemed to suddenly drop dead, without reason.

Bubonic plague is lymphatic in nature and is the most common but least deadly form of plague. It is named for its most infamous symptom, the swollen lumps, or buboes, which grow around the groin, armpits, or neck of victims. These lumps would sometimes weep fluids or explode. These lumps are actually infected lymph nodes located closest to the site where infection occurred, usually due to infected flea bite, like in septicemic plague.

These fleas—and the rats they rode on, as well as the humans they eventually bit—were the animal vectors, or carriers and transmitters of the disease. Vectors had an utterly vital role to play in the spread of plague in all its forms, not just bubonic. While the Y. pestis bacterium can exist dormant in certain environments for years at a time without a host, it is only truly living in its element when it has infected and reproduced through other living things.

Other symptoms of bubonic plague include flu-like conditions, seizures, and gangrene in the extremities, lips, and nose. The blackened appearance of victims’ limbs and faces was very striking and disturbing to early medieval people. It was the most highly visible evidence of disease during the pandemic of 1347-51, and as a result, it eventually lent itself to the name of the Black Death, even if it might not have been the only pandemic disease present during that era.


It is generally agreed upon today that the Black Death was caused by its namesake, bubonic plague, in combination with other forms of plague that appeared more rarely. There is broad support for this theory from both historical and scientific analysis. There are dissenting theories offering alternative explanations for parts of, or the entirety of the pandemic.

These counter-arguments emphasize the similarities between plagues and non-plague diseases, which might have been more likely to spread in the context of 14th century Afro-Eurasia. The arguments also point at certain perceived holes in the bubonic plague theory, each of which will be addressed in full as they appear chronologically. For the time being, a brief list of proposed alternative diseases and their symptoms will be outlined.

Anthrax is a disease caused by the bacterium Bacillus anthracis. It comes in multiple forms and types of infection, like Y. pestis. These include cutaneous (skin), inhalation, and gastrointestinal anthrax. Anthrax spreads via spores and does not require an animal vector to spread person-to-person as plague does. It can also be spread by the consumption of meat from an infected animal.

A common symptom of cutaneous anthrax is swelling skin lesions that eventually turn into blackened ulcers called eschars. These eschars could superficially resemble the buboes of bubonic plague, especially to an uninformed medieval observer. The symptoms of inhalation anthrax are similar to many other respiratory illnesses and could have seemed identical to pneumonic plague. Gastrointestinal anthrax, characterized by abdominal pains, bleeding from orifices, and vomiting or defecating blood, would also resemble septicemic plague.

An extinct form or mutation of Ebola, or an Ebola-like disease, has also been proposed. Unlike anthrax or plague, which are caused by bacteria, Ebola is caused by a virus with a lengthy incubation period. This would allow asymptomatic carriers of the virus to infect many more people before becoming ill. Symptoms, dominated by bodily pain as well as bleeding internally and externally, would also resemble septicemic plague in pre-modern times.

None of these alternate theories are proven. They exist because of a vacuum in modern knowledge of ancient plague pandemics.

All the Rest

Owing to the vagueness of the historical definition of “plague,” as well as early/medieval medical records in general, there have been many disease outbreaks that will probably never be identifiable or confirmed as related or unrelated to Y. pestis. Therefore, they cannot clearly be connected to the continuity of pandemics that gave way to the Black Death. As modern technology and historical epidemiological techniques improve, this will change. For the time being, however, they will only be given a passing mention, to acknowledge that they happened, and to paint the portrait of a past that was filled with diseases, where the Black Death was not an isolated or even unusual event. It was unprecedented and unique for its size and scale, but not necessarily for its content.

Three Pandemics?

The traditional European model for understanding the appearance of Y. pestis on the world stage, developed during the late nineteenth and early twentieth centuries, is that plague has appeared in three “waves” throughout recorded history. These were the First Pandemic, or the Plague of Justinian, beginning in 541 CE, the Second Pandemic, or the Black Death, beginning in 1347, and the Third Pandemic beginning in 1855. The Third Pandemic, sometimes known as the Modern Plague, is beyond the scope of this book to describe in detail, but still merits attention later on.

This Three Plague Epidemics schema is generally considered to be Eurocentric today. It worked well enough for traditional European historiography, when dealing with European history exclusively. It does not capture the full scope of plague pandemics globally, however. The divisions between these three periods become murky and uncertain when one looks at the outbreaks and movements of plague in between them, both outside of and within Europe. The distinction between the Second and Third Epidemics can be especially blurry, as will be shown.

Consequently, this examination of the Black Death will not be limited to what it was originally conceived as. It will bring attention to the changes and continuity present throughout plague’s existence in Afro-Eurasia. It will also present the pandemic in late medieval and early renaissance Europe as one consequence of Europe’s intimate interconnectedness with the rest of the world, rather than as some isolated event unique to the subcontinent. Finally, it will attempt to explain the epidemiology—the study of diseases such as plague—not as a single dogma set in stone, but as a constant and ongoing debate that reaches into the present.

Early Pandemics

In 2018, a gravesite of seventy-eight bodies in Sweden was dated to approximately 3000 BCE. All of its occupants died within two hundred years of each other, making it a fairly large burial site that grew quickly, considering its Neolithic origins. When the DNA samples from the site were analyzed, an ancient and unique strain of Y. pestis capable of causing pneumonic plague was found in the bodies. The grave may have been a dumping ground specifically for the corpses of the diseased.

This is the oldest known evidence of plague in Eurasia, coming slightly before Y. pestis samples were found in the central Eurasian steppe. Both discoveries, among a half-dozen others, precede and overlap with a period of early societal collapse and mass human migration known as the Neolithic Decline. The causes for the decline are still debated, but the presence of plague in such far-flung parts of the continent supports the theory that plague traveled throughout Eurasia on early trade routes, creating an epidemic that contributed to widespread prehistoric collapse.

According to this theory, plague persisted in western and eastern Eurasia until the early Bronze Age, by constantly moving back and forth with migrations and trade goods. Eventually, it went extinct in Europe and lay dormant in Central Asia for centuries. It is unclear how it figures into this prehistoric spread, but an endemic Y. pestis presence in East Africa might have also been established in this time period. As global networks were recreated, plague was coaxed back out into the east and west by the movement of infected animals and people during late Classical Antiquity.

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Areas where a strain of Y. pestis became epidemic and caused outbreaks among local animal vectors over a long period of time are referred to as plague foci, which is to say focuses or “reservoirs” of plague. These foci could lie dormant for hundreds or even thousands of years before being disturbed by significant human or animal activity. Like a cup filled with liquid almost to overflowing, disturbing these foci caused them to spill some of their contents out onto the metaphorical tabletop of the world. Wherever the plague spread and there happened to be a favorable environment, it would “pool up” and potentially create a new plague focus. The prehistoric movements of humans produced countless ‘spills’ like this over the centuries, allowing plague to travel far and wide on the “waves” of animal vectors.

This ancient origin, thousands of years removed from the Black Death, is important to note for sociopolitical reasons. Throughout recorded history, European and later American scholars have ascribed an eastern or, alternatively, African origin or quality to the plague. Sometimes it was purely directional, but other times it was politically or ideologically charged—it was a tool used to target the “other”, to paint different parts of the world as the sources of disease, or even to blame various people for the existence and spread of pandemics.

This can be proven false, thanks to modern DNA analysis and genome sequencing, among a host of other disciplines. There is no identifiable source of the bacterium Y. pestis and it has been freely swapped back and forth across Afro-Eurasia alongside so many other epidemic diseases for so many thousands of years that pointing a finger is a moot point. As history will show, not even Yersinia pestis discriminates between its potential hosts.

The Plague of Athens

In 430 BCE, Greek city-states were embroiled in the Peloponnesian War. Sparta and its allies were very strong land-based powers. This forced their opponents, Athens and allied coastal cities, to rely upon their maritime strength to fight the war and keep vital trade going. As their cities became crowded with starving refugees from the war, an unknown disease appeared in Piraeus.

The disease was highly contagious, especially in cramped and unclean urban conditions. It spread across the eastern Mediterranean, causing widespread death but also throwing Greek social order into upheaval. As much as a quarter of Athens’ population was killed. As would be seen in parts of Europe during the Black Death, lawlessness and a breakdown in basic civility were rampant—at least according to Thucydides, the Athenian historian who chronicled the disease as part of his History of the Peloponnesian War.

Thucydides claimed the disease originated in Ethiopia before spreading through Egypt and Libya—a generic name for all of North Africa at the time. The name Ethiopia meant something different in Ancient Greece from the country we know it as today. It was a semi-mythical place somewhere in the far south and east in the scope of the Greeks’ limited geographical knowledge. It was sometimes considered part of Africa, but just as often thought to be part of India, where many strange and fantastic things were said to originate. Plague was established in the Horn of Africa region at some point, so a north-south transfer may have been plausible.

Thucydides contracted the disease while he was writing his history, so he was able to offer a vivid picture of its symptoms. Fever, inflammation of the eyes, sore or bleeding throat, flu-like symptoms, pustules or ulcers across the body, and insomnia characterized as the so-called “Thucydides Syndrome”.

About three-dozen known diseases have been candidates throughout history, with the traditional theory being that it was bubonic plague proper, or bubonic plague combined with other forms of Y. pestis infection. The late twentieth century saw the emergence of the Ebola theory, citing the (potentially) African starting point of the pandemic and its similar symptoms.

Antonine & Cyprian Plagues

Over five hundred years later, Greece and other parts of the Mediterranean world were firmly under the control of the Roman Empire. In 165 CE, during the reign of Marcus Aurelius Antoninus, another unrecognized disease was introduced to Europe.

According to Galen, the Greek physician who studied the illness, it was brought by Roman soldiers who had recently fought in and around the Levant in West Asia.

The disease was characterized by fever, diarrhea, inflammation of the throat, and growths on the skin that may have been pustules. At its peak, it was killing some two thousand people a day in the city of Rome, and in total, claimed about five million lives across the empire. The Roman military was crippled by it. Marcus Aurelius’ co-regent, the emperor Lucius Verus, might have also died of the disease.

Less than one hundred years after that, a similar or almost identical disease swept through the empire. The plague of 249, as recorded by St. Cyprian of Carthage, killed as many as five thousand people a day in Rome. Throat inflammation or lesions returned as a symptom found in victims of this pandemic. It was joined by vomiting, inflammation of the eyes, necrosis of the extremities, or loss of hearing and sight.

This epidemic brought about such societal breakdown in parts of the empire that huge numbers of formerly polytheist converts flocked to the new religion of Christianity in the hopes of divine protection. It added to the Crisis of the Third Century that eventually divided Rome into three competing states, and almost saw the whole empire’s collapse.

The two plagues resembled one another enough that some experts have suggested they were outbreaks of the same disease. It has been theorized to be smallpox or measles, or a combination of the two in some unknown order. There is no hard evidence for either except that the culprit(s) were probably diseases that the populations of the Mediterranean did not have immunity to at the time. Competing theories suggest a viral origin, such as Ebola. Though they share some symptoms with Y. pestis plagues, it is considered unlikely that either of these pandemics was caused by the bacterium.

The Plague of Justinian

The first uncontested bubonic plague outbreak in recorded European history came three centuries later, beginning in 541 CE. Y. pestis had inched its way back west across Eurasia in half of the first millennium, with sites across the Tian Shan mountains and other sites in Central Asia producing either remnants of the bacterium or early steppe nomads who had been infected by it. The vast web of interconnected steppe politics that caused the Xiongnu confederacy to disintegrate in the east and the Huns to migrate into the west may have also given Y. pestis the push it needed to reach West Asia and the Mediterranean. These bacterium strains were related, though not identical, to the one that was about to hit.

Contemporary sources claimed that the disease came from Egypt. Accounts written by the historian Procopius of Caesarea and others point to the port of Pelusium, near Suez, as the start of the pandemic in Eastern Roman lands. Similar to Thucydides’ account of the Plague of Athens, but without mythical connotations, they claimed that the ultimate origin of the plague might have been distant Ethiopia.

Whatever the plague’s “ultimate” origins, the theory that it entered the Mediterranean Basin via Egypt is very possible. Egypt was the undisputed breadbasket of the Roman Empire at the time, supplying countless major cities and territories with huge shipments of grain, without which they would not be able to support themselves. Prior to distribution and shipment by sea, these grains were stored in huge granaries that made ideal homes for pests. Accordingly, the rat and flea populations of Egypt were vast and fat.

The plague spread quickly after hitting the Mediterranean. It spread in all directions, including westward into Roman Gaul and eastward into Sassanid Persia. According to modern archaeology and scientific analysis, it may have even reached as far as Ireland. The place where it was most infamous—as well as most thoroughly documented—was in Constantinople, the capital of the Byzantine Empire.

The plague struck Constantinople in the spring of 542, where it lasted about four months and was considered to be at its worst for three. It afflicted every social rank and walk of life in the city with little regard for previous health or living conditions.

Even the Byzantine Emperor Justinian I was infected and bore a bubo on his groin, though he survived it. As a consequence of this high-profile victim, the plague of 541-42 is often referred to as the Plague of Justinian, or the Justinianic Plague.

Procopius noted a diversity of symptoms in those afflicted by the plague. An early fever, as well as a swollen bubo toward the end, seemed to be almost universal, but in between these stages, the infection lacked uniformity. Some vomited blood, while others lapsed into deep comas, or entered manic and paranoid episodes of delirium. He claimed a few were left with lisping or incoherent speech after surviving the plague, described in his words as their tongues having been “affected”. It is also possible that slurred speech was a consequence of brain damage from the fever.

The duration of the infection varied from person to person. Some were said to die within a day of contracting the fever even without any visible buboes forming, while others could languish for days, perhaps a week or more. It was apparently a good indicator of recovery when a victim’s buboes ruptured with pus.

It is unknown how many people this plague actually killed during its initial sweep. Procopius styled his chronicle on the plague after Thucydides, with its mix of factual observation and hyperbole. He claimed that as many as ten thousand people died every day in the streets of Constantinople at the plague’s height. He claimed that there was not enough space or manpower to manage all of the corpses, so they remained unburied in stacks in the streets, making the city reek of death. He claimed that the plague came close to annihilating the human race, treating the conditions in the city as if they were the norm everywhere else in the world. Obviously, this was not the case.

What is known is, this was only the first “wave” of what is classified as the Justinianic Plague. This strain of the plague, or genetic offshoots of it, did not fully dissipate after the first wave ended in 544. Instead, they went dormant and became epidemic in their particular areas of West Eurasia. For the next two centuries, they would continue to flare up into major outbreaks every few decades. Estimates for the number of waves are between fourteen and twenty-five.

The traditional estimate was that anywhere from twenty-five to one hundred million people died between 541 and 750. This maps to about half the population of the Mediterranean and Europe, according to our current demographic knowledge. These figures are considered exaggerations today, though by how much is a matter of debate.

The lack of detailed accounts for most of the later waves of Justinianic Plague suggests that they were less deadly than the first narrated by Procopius. Procopius’ original account only made up a tiny minority of the history he wrote, suggesting that, apocalyptic prose aside, the plague was not quite as bad either. As successive generations gained resistance to the increasingly localized disease, deaths would naturally drop as well.

The plague in Iran was also destructive, but in the order of hundreds of thousands of deaths total, rather than millions. Justinian was not the only head of state afflicted with the disease—in the wave of 627, the Sassanian Shah Shiroyeh died alongside one hundred thousand of his subjects in the capital of Ctesiphon. The successive waves cut short in the Greater Iran region long before they did in the Mediterranean, however.

After 689, there are no records of epidemics or pandemics resembling bubonic plague in Iran. Y. pestis must have continued to exist in the region, however, because it would flare up again in 1270—many centuries after the cutoff date for the Plague of Justinian, but well in advance of even the earliest Black Death dates. The “three epidemics” model begins to resemble more of a continuity that waxes and wanes, but never fully vanishes.

Modern analysis of sixth to eighth-century records also paints a picture of an Eastern Roman Empire which was wounded, but then recovered and remained relatively stable. Surviving records of taxation, land use, coin issue, and general economic vitality don’t support the theory of as much as half of the continent being wiped out. This also undermines the theory that the Justinianic Plague was a major or even direct cause of the fall of the Roman Empire as a whole. The records only cover the lands of the Byzantine and Sassanid Empires, but those lands also included the largest population centers in western Eurasia at the time, meaning that the presence or absence of plague in other areas such as the Germanic kingdoms of formerly Roman far-western Europe would not have greatly skewed the death toll.

The World on The Eve of The Black Death

The borders between historical periods are always fast and loose, but somewhere between the beginning and the end of the Justinianic Plague, the world moved out of Late Antiquity and into the Post-Classical Era. For Europe, that meant transitioning from the Classical Period to the Middle Ages. The period during and after the fall of the Western Roman Empire is often regarded as the “Dark Ages” for its perceived decline in safety, progress, knowledge, and prosperity. Post-Roman Europe was full of crises and challenges where existing institutions had to undergo massive change or die out completely. Yet it was not quite as “dark” as believed.

Knowledge was lost, but people did not lose their naturally inquisitive and curious edge. Innovations, which were forgotten, were gradually rediscovered. Existing knowledge from the classics was preserved and reproduced in Christian monasteries and emerging Muslim madrasas, certainly not accessible to the vast majority of people, but also not lost to civilization as a whole. Wars became more frequent and regionally endemic, but also much smaller than the massive, destructive scale of wars that had been fought for or against the Roman Empire. Mutual trade and cultural exchange across geographic and religious boundaries shrank at first, but then resumed—and it was not primarily thanks to some Crusaders coming home and telling stories of the “riches of the Orient”.

As faint a silver lining as this is, the approaching second of the three plague pandemics indicated how well medieval Eurasia had been doing in the centuries beforehand. It had to be very healthy and vigorous in order to contract and spread the plagues as bad as it did, in the way that it did, in a few more centuries. In order for the Black Death to hit, there had to first be life.

The Great Famine

That is not to say that the 1300s were completely prosperous up until the Black Death. Part of the explanation for why Europe appeared to be hit so much harder than the rest of Eurasia is that Europe was primed for plague infection a few decades earlier. From 1315 to 1317, a change in weather was caused by the end of the Medieval Warm Period. This damaged the growing seasons in Europe and caused crops to fail repeatedly. At the same time, a series of murrains—livestock disease outbreaks—killed nearly eighty percent of sheep and cattle in Europe. Starvation set in, and mass death and disorder followed soon after.

The exact numbers are even more poorly understood than in the Black Death that followed, but experts estimate that anywhere from one-tenth to one-quarter of Europe’s population died from the Great Famine. Fertility dropped sharply, meaning that population growth also slowed. The average life expectancy among literate elites in England dropped to less than thirty years, and that number was probably even lower among the poor and in other parts of Europe.

The worst crop failures ended after 1317, but the effects of the famine lingered until 1322 before agricultural yields started to balance out again. The survivors were less healthy than those who had lived a generation before. Compromised immune systems and weakened governments would have made Europeans more vulnerable to any pandemic, and they were unlucky enough that it was a plague.

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