What Was the Scientific Cause of the Black Plague?


The Black Plague, which is also known as the Black Death or the Bubonic Plague, was one of the most fatal pandemics in human history, killing an estimated 75-200 million people across Eurasia in the 14th century. People thought for ages that the epidemic was caused by divine punishment or foul air. Researchers were able to discover the actual cause, a bacterium called Yersinia pestis, thanks to breakthroughs in scientific understanding. In this essay, we’ll look at the scientific origin of the Black Plague, how it spread, and how it affected human civilization. Prepare to enter the intriguing world of microbiology and epidemiology, which led to one of history’s deadliest diseases.

How the Black Plague Started

The Black Plague was not a sudden, isolated outbreak in 14th-century Europe. Instead, it was a pandemic that had been spreading for ages via the Near and Far East trade routes. Before the “death ships” arrived in Messina in 1347, stories of a “Great Pestilence” devastating havoc in the East had circulated throughout Europe.

By the early 1340s, the plague had already decimated several countries in Asia, including China, India, Persia, Syria, and Egypt. The first epidemic of the Black Plague is thought to have occurred in the 1330s in the Chinese province of Hubei. It spread to other parts of Asia, most likely by merchant ships traveling along the Silk Road and other trade routes.

In 1347, the Black Plague spread from China and Inner Asia to the Genoese trading town of Kaffa in Crimea. During the siege of the port by the Kipchak ruler Janibeg, he threw plague-infested corpses into the town. The disease was then carried westward by Genoese ships to Mediterranean ports, where it spread throughout Europe. It arrived in England in 1348 and swept over the kingdom, wreaking havoc on London, East Anglia, and Yorkshire in particular. In 1350, the Black Plague reached the far north of England, Scotland, Scandinavia, and the Baltic kingdoms.

Recurrences of the plague occurred in Europe in 1361-63, 1369-71, 1374-75, 1390, and 1400 and were most likely transported from Central Asia via trade routes. The rate of mortality from the Black Plague fluctuated, with some areas escaping lightly, such as Milan, Flanders, and Béarn, while Tuscany, Aragon, Catalonia, and Languedoc were severely devastated. The towns were hit worse than the countryside, and monastic communities were hit the hardest. Even the wealthy and powerful were not immune to the disease, as several royals and significant persons died from it.

The spread of the Black Death in Europe, North Africa, and the Near East (1346–1353)

The Symptoms Experienced by Black Plague Patients

When the plague arrived in Europe, it quickly spread, killing millions in a short amount of time. Europeans were unprepared for the atrocities caused by the Black Plague. The symptoms were alarming and caused a lot of pain. Many individuals were taken aback by the magnitude of the outbreak and the sheer quantity of deaths.

The symptoms of the Black Plague were vividly described by the Italian author Giovanni Boccaccio. The sickness started with weird swellings in the groin or under the armpits that quickly swelled to the size of an apple or even an egg. These “plague-boils” leaked blood and pus and were frequently associated with fever, chills, vomiting, diarrhea, and severe pain. In most cases, death occurred soon after the onset of these symptoms.

Because it affected the lymphatic system, the Bubonic Plague was very lethal. This caused the lymph nodes to expand, forming the infamous “plague boils.” If the infection is not treated, it can spread to other body regions, such as the blood or lungs, resulting in a faster and more painful death. The rapid spread of the Black Plague was partly due to people’s lack of awareness of how the disease was communicated or how to prevent it.

The Biological Cause Behind the Black Plague

Scientists have identified the bacteria Yersinia pestis as the source of the Black Plague, often known as the plague, in the modern era. In the late 1800s, a French researcher named Alexandre Yersin identified the germ. They later determined that the bacterium may be passed from person to person via the air and also through the bite of infected fleas and rodents. These pests were ubiquitous in medieval Europe and were frequently found on ships, allowing the plague to move quickly from port city to port city.

The Black Plague first devastated Messina, and it quickly spread to Marseilles in France and Tunis in North Africa. Rome and Florence were quickly impacted as two cities at the crossroads of a vast network of commercial routes. The epidemic had reached important towns such as Paris, Bordeaux, Lyon, and London by the middle of 1348.

No rational explanation existed for the Black Plague’s quick spread and enormous mortality rate in the 14th century. People didn’t understand how the disease spread from person to person, and they didn’t know how to prevent or treat it. Some doctors even claimed that “instantaneous death occurs when the aerial spirit escaping from the eyes of the sick man strikes the healthy person standing nearby and looking at the sick.” It took a long time for scientists to discover the bacterium responsible and create treatments and preventions.

Oriental rat flea infected with the Yersinia pestis bacterium

Black Plague Was Thought to be “God’s Punishment”

The medieval mindset was profoundly imprinted with the concept that the Black Plague was retribution from God. People interpreted the outbreak as a portent of divine anger, and they sought ways to satisfy an enraged God. This included hunting for scapegoats to blame for the outbreak in some circumstances. Many individuals saw Jews, who were already disadvantaged in medieval Europe, as an accessible target. Anti-Semitism was widespread, and stories persisted that Jews were to blame for the disease’s spread by poisoning wells and springs.

As a result, Jewish communities throughout Europe faced violence and persecution. In certain cases, entire communities were destroyed, and synagogues were destroyed. Many Jews were forced to evacuate their homes and seek asylum elsewhere in Europe. Others dealt with the epidemic’s anxiety and uncertainty by focusing inward and on their spiritual well-being. The belief that the Black Plague was God’s judgment for humanity’s misdeeds caused many people to evaluate their own lives and repent of their own wickedness.

Some people turned to religious activities like fasting, prayer, and flagellation to demonstrate their piety and seek God’s pardon. Others went on pilgrimages to holy destinations or gave to churches and religious groups. Others abandoned faith entirely, believing that the pandemic was proof that God had abandoned humanity. In the face of an apparently pointless and harsh world, these people turned to hedonism and indulgence, seeking pleasure and happiness.

Jews being burned at the stake in 1349. Miniature from a 14th-century manuscript Antiquitates Flandriae by Gilles Li Muisis

How Was Black Plague Treated Back Then

Medical knowledge and treatment choices were severely limited during the Black Plague outbreak. Because physicians lacked a thorough grasp of the disease’s biology, they depended on treatments such as bloodletting and boil-lancing, which were not only ineffectual but also harmful and unhygienic. Bloodletting entailed severing a vein to drain blood from the body with the hope of restoring balance and eliminating the sickness. Boil-lancing entailed opening the plague boils and allowing the pus to drain.

To fight against the disease, many individuals turned to superstitious customs such as burning aromatic plants and soaking them in rosewater or vinegar. Some even claimed that donning a mask or carrying a bag full of fragrant herbs would protect them against the disease.

In addition to inadequate treatments, healthy individuals frequently avoided sick persons in a panic. Doctors and priests refused to see patients or perform last rites, and shops closed their doors. Many people evacuated the city for the countryside with the aim of avoiding the sickness totally, but this proved difficult. The disease impacted not only humans but also animals, resulting in wool scarcity in Europe due to the massive death of sheep.

A plague doctor and his typical apparel during the 17th-century outbreak

Does the Black Plague Still Exist Today?

Bubonic plague is not a bygone era; it still exists in the present world. While the epidemics are far smaller and more controlled than they were during the Black Plague years, they remain a major public health risk.

The disease is endemic in various African countries. Thus the majority of cases today occur there. In Madagascar, for example, outbreaks of bubonic and pneumonic plague occur virtually every year. The Democratic Republic of the Congo, Peru, and Bolivia are also affected by the endemic plague.

Each year, seven cases of plague are reported in the United States. Despite the low number of instances, the disease remains a worry due to the potential for serious sickness or death if not treated promptly.

The majority of occurrences in the United States occur in two areas: the Southwest’s Four Corners region (which includes parts of Arizona, Colorado, New Mexico, and Utah) and California’s Sierra Nevada region. Fleas that infest wild rodents, such as prairie dogs, squirrels, and chipmunks, carry the disease in these places.

Fortunately, contemporary medicine is far more suited than medieval medicine to deal with cases of bubonic plague. If the disease is detected early enough, antibiotics such as streptomycin and gentamicin can be quite helpful in treating it. There are other vaccines available to prevent persons who are at high risk of infection, such as laboratory workers and travelers to endemic areas.

The Black Plague was one of the deadliest pandemics in human history, claiming the lives of millions of people across Europe and beyond. The bacteria Yersinia pestis caused the disease, which was carried through the air and by fleas on rats. Despite the horrors of the Black Plague, it fostered medical and public health breakthroughs that have helped avert future outbreaks. While incidences of bubonic plague continue to occur today, breakthroughs in science and technology have enabled better diagnosis, treatment, and prevention. Understanding the scientific etiology of the Black Plague has been critical in combating the epidemic and will continue to be critical in the ongoing attempt to manage it.

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