Introduction

The Black Death was a global epidemic of primarily bubonic plague caused by a bacterium that killed over 70 million people in Europe during the mid-1300s. It is one of the most fatal plagues in history, killing an estimated 50% of Europe’s population and having serious effects on trade, labour, and the economy.¹ This article will discuss the spread and origin of the plague, its symptoms and impact on society as well as the lessons learnt from the disease.

Origin and spread from Central Asia 

The Black Death was caused by an infection of the bacterium Yersinia pestis. It was thought to have originated in China and inner Asia during 1346. At the time, Central Asia had a high rodent and flea population, especially around the Caspian Sea. This allowed the bacterium to survive and spread, while the semi-arid climate supported the maintenance and spread of the disease. 

Central Asia was also part of a critical and extensive trade network known as the Silk Road which connected the East to the West facilitating trade and the rapid spread of the disease. As a result, the plague was then quickly spread westward by fleas and rats on trade ships where it was able to reach Mediterranean ports. From there it spread across northern Africa, and mainland Europe including Italy, Spain and France by 1348. 

The plague is then thought to have reached the UK on a ship arriving at the Dorset coast from Gascony in France. The first reported death in England was in June of 1348, and from there it continued to spread rapidly reaching Scotland and the Baltic countries by 1950. The Black Death also had small outbreaks in Russia and southern Africa. However, these were much less affected than Western Europe. The disease also did not reach the Americas.^1,2,3

Symptoms and transmission

The bacterium Yersinia pestis which caused the black death, has three primary forms of infection: bubonic, septicemic, and pneumonic plague.¹

Bubonic plague

The Bubonic plague is transmitted through the bites of infected fleas, which typically infest rodents such as rats. The infection causes swollen and painful lymph nodes, known as buboes, along with fever, chills, headache, and fatigue. The bubonic form of the plague was the most common. It caused severe illness and death with around a 60% mortality rate. Despite transmission between humans being rare it accounted for the majority of deaths.

Septicemic plague

The Septicemic plague was the least common of the three forms during the 14^th century. It occurred as a primary infection by direct entry of the bacteria into the bloodstream or often a progression of untreated bubonic or pneumonic plague. The symptoms included fever, chills, extreme weakness, abdominal pain, shock, and bleeding into the skin and other organs. It could cause blackening and death of tissue (gangrene) in extremities, such as fingers, toes, and the nose. The mortality at the time was nearly 100%.

Pneumonic plague

The pneumonic plague is the most virulent form and occurs when the Yersinia pestis bacterium infects the lungs, either through inhalation of respiratory droplets from an infected person or as a complication of untreated bubonic or septicemic plague. The symptoms include fever, coughing, chest pain, difficulty breathing, and bloody or watery sputum (the mucus made in the lungs). 

The Pneumonic plague is highly contagious and can be transmitted from person to person through respiratory droplets. It is the only form of plague that can spread directly from human to human and had nearly a 100% mortality rate during the 14^th century. Buboes are not present in the pneumonic plague, but if the bubonic plague is not treated, the bacteria can spread throughout the bloodstream and infect the lungs, which can cause a secondary case of pneumonic plague.^1,4,5

Impact on European Society

The Black Death had a profound impact on European society. Due to the massive death toll, there were significant changes to Europe’s demographic, population distribution, economy, and social structure which had long-lasting effects. Some of these changes were:

Depopulation of rural areas: The plague caused many rural villages to be completely wiped out (around 1,000 villages were thought to have completely disappeared). This led to a lack of skilled labour for agriculture and the migration of rural communities into cities

Decline in agriculture output: The decline in the number of farmers lead to food shortages and economic instability.

Collapse of the feudal system: The feudal system was the hierarchal social and economic structure characterised by land ownership by kings and lords with serfs and peasants that would work on the land for the benefit of the lords. Due to the declining populations, labourers sought better economic opportunities, they had more bargaining power and were able to drive up wages.

Crisis of faith: The extent of death and crisis led to many questioning their religion.⁴

Halting of conflict: While there were no ongoing conflicts at the time, there was a general cessation and reduction in military conflicts.

Responses to the Black Death

The medical response to the black death was poor. The discovery that germs could cause disease was not made until the 1800s. Many people had theories that poor sanitary habits and smell caused the disease, while others thought it was an imbalance between the four houmous (the four elements that mediaeval people thought made up the body: blood, phlegm, black bile and yellow bile). Meanwhile, many people believed in religious or supernatural causes. The medical responses included:

• Fines were introduced for people dumping waste into streets and jobs were created for people to clear waste as many thought the disease spread through smell. This may have helped reduce the number of rats and made a small difference
• Many doctors believed drilling the head would release the evil spirits that caused the plague. Some doctors did burst the buboes of patients with bubonic plague and there is some evidence that this may have helped increase the chances of survival, however, it often led to further infection
• Many plague doctors themselves wore distinctive outfits, which included a long, waxed overcoat, gloves, boots, and a wide-brimmed hat. The most notable feature was the beak-shaped mask filled with aromatic substances, thought to protect them from miasma (bad air), which was believed to cause the disease
• Bloodletting was performed to draw blood from the patients to balance out the four humours
• Quarantine (40 days of isolation) was introduced for arriving ships., This was long enough for the infected fleas transmitting the disease to die. However, this wasn’t always implemented effectively⁵

Many doctors fled from cities; however, one French doctor did identify the two main types and symptoms of the bubonic and pneumonic plague. Little, however, was learnt from the Black Death as nobody knew what caused it. Consequently, there were a number of further outbreaks, such as that in 1665, that particularly affected London. The exact reason for the eventual decline in deaths from the plague is thought the be due to  a range of reasons including:

• Demographic changes from the higher number of deaths altered disease transmission and limited its spread
• Weakened strain – over time the bacterium may have evolved to become less virulent and cause milder diseases to therefore increase its spread without killing as many people

Disruption in trade routes could have limited spread as well.⁵

FAQ’s

Why is it called the Black Death?

The “Black Death” has several origins, the main being that the disease caused black swelling and dark spots on the skin. The plague itself was never called the black death during the 14^th century. It wasn’t until historians during the 18^th century started to describe the plague did it got the name. The name then began gaining popularity due to its power and association with the dramatic nature of the disease.

Is this plague still a risk today?

While the plague is still present and potentially dangerous in some parts of the world, it is much less of a threat today due to advances in medical treatment, antibiotics, and public health measures. The risk of widespread pandemics like the Black Death has been greatly reduced, but localised outbreaks do occur and require prompt attention and management to prevent spread.

When was the plague bacteria discovered?

In 1894 Alexandre Yersin discovered the plague and the bacteria was named after him “Yersinia pestis”.

Summary

The Black Death was one of the biggest pandemics in history. Originating in Central Asia and eventually spreading west. It was caused by the bacterium Yersinia pestis, the bubonic form of the plague being the most common. Symptoms include swollen lymph nodes, skin discolouration and fever among other signs. The plague greatly changed the population’s demographic, social structures, and economy.