The Black Death

The 'Black Death' is another name for the plague, a disease caused by a tiny organism (or bacterium) called Yersinia pestis. There are two main stages. Septicaemic plague infects the blood and lymph glands, and then pneumonic plague infects the lungs.

The illness first causes an acute fever, developing rapidly into pneumonic plague, which is untreatable. Symptoms two to nine days after infection include:

• Fever, headaches and chills
• Exhaustion and delirium
• Swollen, painful, and sometimes hot-to-the-touch lymph nodes called ‘buboes', (hence the name ‘bubonic plague')
• Septicaemic blood infection and a 60% chance of death
• Coughing blood
• Lung infection, usually causing death in one to three days

In the 14th century, people did not understand the disease, but they were familiar with the symptoms. Their descriptions of the plague outline symptoms that modern doctors would recognise.

It is traditionally believed that the disease got its name from the blackened and putrefying flesh of its victims. However this does not happen. The 'buboes' caused by septicaemic plague show up as purple or black blotches. But bubonic or septicaemic plague was not common in the 14th century. Other stories link the disease to a black comet, a man on a black horse, or a black giant striding across the country.

The most likely origin of the term is as a mistranslation of the Latin expression for the plague: pestis atra or atra mors. 'Atra' is translated as 'dreadful/terrible' but can also mean 'black'.

There is no evidence that the term "Black Death'' came into common use before the 18th century. It was then used to differentiate between the plague of 1348-50 and the Great Plague of London in 1665.

During the 14th century, people thought the plague might be caused by:

• Harmful fumes and vapours emitted during earthquakes or volcanic eruptions
• Supernatural influences, such as God's anger at people's sins
• Astrology such as unlucky planet alignments or a comet
• Contagion: the passing of disease by touching the body, clothing or goods belonging to the victim

It is now known that the plague is a bacterium mainly infecting rodents, particularly black rats. It was passed from one rat to another by rat fleas. Large numbers of infected rats died. The fleas turned to other sources of food: humans.

Pneumonic plague can be passed directly from person to person by water droplet infection. It can be transmitted when the infected person coughs.

The plague bacterium occurs naturally in wild rats. During the 1320s the disease flared up in the Gobi desert of Mongolia. It gradually spread along trade routes, infecting much of Asia.

European merchants were trading with the East, buying spices and silks. It is likely that the plague moved with their trade caravans, travelling from Baghdad to trading stations in the Crimea. From there it rapidly spread across Europe.

A 14th-century chronicle records the plague's arrival in 1348:

'two ships, one of them from Bristol, came alongside. One of the sailors had brought with him from Gascony the seeds of the terrible pestilence and, through him, the men of that town of Melcombe were the first in England to be infected.'

Many ports in southern England were in almost daily contact with the continent. It is likely that plague entered Britain through most of these ports. By 1349, nearly every town and village in Britain had been affected.

Some people think the ‘Black Death' killed a quarter of the European population: around 25 million people. Medieval records suggest that between 17,000 and 50,000 Londoners died. It is impossible to calculate the exact number as there are no accurate records from that time.

Modern historians think that up to half of London's population may have been killed, equalling around 500,000 people. That's ten times higher than people thought at the time!

Plague has never completely left Britain. Possible factors that may have stopped the 'Black Death' are:

• Infected rats died, reducing the food source of the bacterium
• Infected people survived and became immune to the disease
• The bacterium becoming weaker

The last outbreak of plague in London was in 1665-6, now known as the Great Plague. The disease is still common in some parts of the world.

Department of Archaeological Collections and Archive, Museum of London (ed. Jane Sarre)
August 2002

Visit the Museum to see...

The Medieval London gallery. Click here for a map showing the gallery location.

Visit these websites...

Information on the plague from the U.S Department of Health

More detailed information on the bacterium Yersinia Pestis from the Virtual Museum of Bacteria