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Study of the Causes of the Plague Epidemic

The plague epidemic was the deadliest disease in the Middle Ages in Europe. Plague is an acute infectious disease from the group of zooanthroponoses caused by Yersinia Pestis (Stoppler, n.d.). The transmission of the pathogen occurs mainly through a transmissible route from sick rodents. Of most significant importance as a source and reservoir of infection in nature are rats, hares, rabbits, ground squirrels, and marmots. People infected with plague from animals become sources of the anthroponotic direction of the spread of the disease. One of the main reasons for the plague’s spread was climate change.

The mechanisms and routes of infection determine transmission factors. Blood-sucking insects are the main instrument of the spread of plague (most often fleas). As for the contact transmission route, the factors can be the skins of infected animals and various secretions and tissues. Finally, with the airborne mechanism, the transmission factor is the air medium containing the pathogen located in the droplets of mucus secreted by the patient with pneumonic plague and suspended in the air.

Pulmonary forms of plague are the most dangerous in the epidemiological respect since the mechanism of transmission of the pathogen is airborne. At the same time, this form of plague is also the most transient, leading to death in the overwhelming majority of cases. As noted above, primary pulmonary and secondary pulmonary forms of plague are distinguished. Human cases of primary pulmonary plague have also been observed with the disease contracted from domestic cats. Human lice and ticks can also send the infection from person to person. A sick person can, under certain conditions, become a source of infection: with the development of pneumonic plague, direct contact with the purulent contents of the plague bubo, and also as a result of infection of fleas on a patient with plague septicemia. With airborne transmission, the primary pulmonary form of plague develops, if untreated, the mortality rate reaches 30% -60% (Plague, 2019). Thus, the respiratory form of the disease can be fatal to humans in a short time.

Given the different forms of transmission of the disease and the complexity of treatment, it is worth mentioning the effect of the plague on the population of Europe. Clinical research and the elimination of drugs capable of curing the plague began only at the beginning of the 20th century. During the epidemic of the 14th century, quarantine remained the primary way to fight the virus (Jillings, 2018). However, quarantine was not introduced in all cities, which was a massive mistake in the fight against the “black death” (Jillings, 2018). Thus, in four years, Western Europe has lost about 20 million people (Jillings, 2018). The mortality rate among the diseased was 70-80%, and in some places, it even reached 100% (Jillings, 2018). In particular, during the second pandemic, the population of the city of Marseille became utterly extinct. In total, since 1348 in France, about 40% of the population died from the plague in 70-80 years (Jillings, 2018). Germany and England also suffered significant losses during the second pandemic. Only in Bremen (Germany) alone, did the epidemic take away more than 2/3 of the population, and the British Kingdom lost about 1/3 of its inhabitants (Jillings, 2018). The significant number of deaths from the plague, according to the chroniclers, was obviously due to the lack of real personal protective equipment in the society of that distant time, as well as the lack of elementary conditions to counter the mortal danger.

The medicine level in medieval Europe did not allow people to cope with the plague. However, recently, scientists have made several discoveries. The plague microbe is sensitive to many sulfa drugs and antibiotics but is resistant to penicillin, as it forms penicillinase. It is important to emphasize that the plague microbe does not have its multidrug resistance plasmids (Bubonic Plague: Symptoms, Causes, Treatment, Prevention, 2020). One of the reasons for this may be that plague is a blood-borne infection with a vector-borne transmission mechanism. These two circumstances allow the plague microbe to avoid contact with the main reservoir of R-plasmids in nature – intestinal bacteria.

In the XIV century, Europe entered the so-called Little Ice Age, known from the chronicles and chronicles of that time. The discovery itself does not look like a significant scientific breakthrough if one does not know exactly how these data were obtained (Barnes, 2019). Scientists have determined that the glacier’s location and the thickness of its ice cover are a unique natural “archive” of climate change in Europe for thousands of years. The cause of high mortality during the “first plague wave” of 1347-1351 was the weakened health of Europeans, undermined by cold and hunger: the epidemic was preceded by a series of lousy harvest years caused by a general cold snap and high humidity. Data on the amount of precipitation confirmed the assumption that the increase in climate humidity contributed to the rise in the fleas population – the leading carriers of the plague bacillus. Therefore, climate change was one of the reasons for the spreading of the plague.

The plague was the most dangerous disease in medieval Europe, killing a third of the population. The most common mode of transmission of the disease was by rodents and flea bites. The most dangerous form of plague is pneumonic, which is transmitted by airborne droplets. The main problem in counteracting the disease in the Middle Ages was untimely measures taken and the lack of medicines.


Barnes, A. M. (2019). Plague. In Handbook of ZOONOSES (pp. 93-112). CRC Press.

Bubonic Plague: Symptoms, Causes, Treatment, Prevention. (2020). Web.

Jillings, K. (2018). An urban history of the plague: socio-economic, political and medical impacts, 1500–1650. Routledge.

Plague. (2019). Web.

Stoppler, M. (n.d.) Plague (Black Death). Definition, Symptoms, Types, Treatment, History. Web.

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