The Black Death still causes debate among the scientific community.
Pandemics are diseases that spread throughout several countries, and/or that affect a large percentage of the population. The fear of pandemics is increasing, at a time when globalization and climate change make it difficult to control the spread of disease.
In this article we will comment on a classic pandemic, known to the whole world by hearsay, but whose characteristics are unknown to most. We will talk about the Black Death, a disease that made its appearance in the 14th century and hit practically all European countries, with disastrous results for its population.
What was the Black Death
Between approximately 1348 and 1356, a lethal disease made its appearance in Europe, which decreased the continent’s population by between 35 and 60% . This epidemic today is known as the Black Death, whose effects strongly marked the old continent at a demographic and cultural level.
The seriousness of this disease becomes obvious if we study the historical records left to us by the various European writers who lived with the disease. In England, the first wave of plague wiped out nearly half the population in less than 18 months .
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What caused the Black Death
The causes of this epidemic are several. Not only the guilty pathogenic microorganism, but also various climatic and sociological factors, together with the total ignorance of the causes and treatments for this disease, were the cause of its high mortality and dissemination throughout the European continent.
The Black Death was a disease that caused the appearance of buboes, subcutaneous lumps that appeared mainly in the groin and armpits of those affected. Hence one of the names of this disease, the “ bubonic plague ”.
In addition to the appearance of buboes, this disease caused several symptoms such as fever, extreme thirst, muscle pain, vomiting, diarrhea, depression, headache, and confusion. Only 2 out of 5 infected individuals survived the disease , the rest died within a short period of two weeks.
There was also another variant of this disease, called pneumonic plague, which affected the lungs directly and had a mortality close to 100%. We will talk about both variants as well as their differences later in the article.
Below, we summarize some of the main causes of the pandemic that are currently being considered.
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Yersinia pestis, the pathogen
Yersinia pestis is a bacterial pathogen of the bacillary type (which has the shape of a baculum or rod), discovered at the end of the 19th century. This bacillus was discovered by a student of the famous Louis Pasteur, named Alexandre Yersin .
Alexandre Yersin discovered this bacterium while studying a plague epidemic that spread across Asia in the 19th century, where he quickly drew parallels between the epidemic he was studying and the famous European Black Death of the 14th century, since the Asian disease had similar symptoms. to those of the Black Death, including the appearance of buboes.
This bacterium is spread by fleas that feed primarily on the blood of wild rodents . These wild rodent populations, however, can be displaced from their natural habitat and come into contact with groups of rodents that live closer to human populations, which will end up bringing this disease to us.
Y. pestis multiplies inside the body of rodents, but once a flea absorbs this bacteria into its interior, Y. pestis will gobble up most of the nutrients the flea would normally feed on . This causes fleas affected by this bacteria to forage more aggressively.
At the moment that the flea tries to feed on another animal, Y. pestis forces the flea to vomit blood contaminated by the bacteria itself into the wound that the flea has just produced to feed. In this way the bacillus enters another mammalian body, where it will look for the lymphatic vessels and nodes to multiply freely. This is due to the appearance of buboes .
After colonizing the lymphatic system, the bacterium moves to the blood to infect various organs of the affected person, causing the rest of the symptoms of the disease. In cases of pneumonic plague, Y. pestis does not use fleas for its propagation. Instead, it will take advantage of the cough of those affected to directly infect the lungs of the next victim, causing a more serious and deadly disease.
Although Y. pestis is accepted as the main culprit of the Black Death, there are differences between the symptoms of the Asian bubonic plague epidemic and the plague described in the 14th century. This has caused some doubts within the scientific community about whether Yersinia is really the cause of the disease . Even so, the arguments that defend her as a possible culprit are solid, and include:
- DNA evidence of Yersinia in corpses from mass graves of the 14th century.
- Genetic and metabolic differences between the bacteria of the different epidemics
How it wiped out the European population
In addition to the disease itself, to understand the incredible scope of the 14th century pandemic, we must take into account other factors. If Y. pestis is a common pathogen in wild Asian rodents, we also need to explain how it got to Europe .
Wild rodent communities in the Central Asian plains had been displaced to urban centers by droughts and earthquakes that altered their natural habitat. This caused the spread of the disease to rodent communities that lived with humans, and then spread to humans throughout Asia and then Russia.
This expansion throughout the Asian continent would explain the double path of arrival of the Black Death in Europe, where it would have devastating effects due to the overpopulation that this continent experienced .
1. By sea
The maritime route of transmission of the Black Death is explained by the growing commercial contact between Asia and Europe during the 14th century. The fleas capable of carrying the disease are capable of living for 6 weeks without feeding on any animal, which facilitates their transfer between ports .
In about 1347, the disease would reach Italy by sea . The mercantile maritime routes of the Mediterranean would be in charge of spreading the disease along all the European coasts, from the Dead Sea to the north of Spain.
2. By land
The overland route of expansion of the Black Death occurred in part because the troops of the Golden Horde, the former Mongol empire, were affected by the disease while attacking Europe.
This army had no qualms about using the corpses of soldiers who died from the disease as a siege weapon , as happened in ancient Genoa. This city, during its siege by Mongol troops, had to withstand the rain of infected corpses that the attackers threw over its fortifications, which spread the disease between the city walls.
Those Genoese who escaped the siege also inadvertently contributed to the spread of the disease in its early stages.
The bubonic plague and other current epidemics
Bubonic plague is still a disease that occurs today, especially in rural areas that come into contact with infected rodent populations. The multitude of climatic, demographic, biological and social factors that were coordinated so that the severity of the Black Death was such, will hardly be repeated .
Still, catastrophes like this keep us on our toes. There are other diseases today, such as some types of flu, that could have a catastrophic impact on our population . It is important that we understand the epidemiological factors of diseases, not only to avoid those that we know about, but also to prevent those that may appear by surprise.
Climate change will cause changes in migratory routes and habitats of different animals, as well as massive migrations of populations from countries with few resources or affected by natural disasters. If we are not vigilant, a new epidemic could loom over our globalized world, just as the plague did with Europe in its day.
Bibliographic references
- Horrox, R. (2007). The Blackdeath. Manchester: Manchester University Press. ISBN-13: 9780719034985.
- Haensch S, Bianucci R, Signoli M, Rajerison M, Schultz M (2010). Distinct clones of Yersinia pestis caused the black death. PLoS pathogens, 6(10), e1001134. doi:10.1371/journal.ppat.1001134.
- Stenseth NC, Atshabar BB, Begon M, Belmain SR, Bertherat E (2008). Plague: past, present, and future. PLoS medicine, 5(1), e3. doi:10.1371/journal.pmed.0050003.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.
