Black Death

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The Black Death was a devastating epidemic in Europe in the 14th century which is estimated to have killed about a third of the population. Most scientists believe that the Black Death was an outbreak of bubonic plague, a dreaded disease that has spread in pandemic form several times through history. The plague is caused by the bacterium Yersinia pestis which is spread by fleas with the help of animals like the black rat (Rattus rattus). Sometime, the term "Black Death" is used for all outbreaks of plague.

There is evidence that there were outbreaks of the plague in Europe in the 6th century. The last major outbreaks there occurred in Britain in the latter half of the 17th century (see Great Plague) and on the Continent in the first quarter of the 18th century. The plague still exists elsewhere, but can nowadays be treated effectively with antibiotics.

It is not entirely clear where the major epidemic of the 14th century started, but it was probably somewhere around the northern parts of India. It then spread west to the Middle East. The plague was imported to Europe by the way of the Crimea, where the Genoese colony Kaffa (Feodosiya) was besieged by the Mongols. Myth (or history?) says that the Mongols catapulted infected cadavers into the city. The refugees from Kaffa then took the plague along to Messina, Genoa and Venice, around the turn of 1347/48. Some ships didn't have anyone alive when they reached their port. From Italy the disease spread clockwise around Europe, hitting France, Spain, Britain, Germany, Scandinavia and finally north-western Russia around 1351.

The information about the death toll varies widely from source to source, but it is estimated that about a third of the population of Europe died from the outbreak in the mid-1300s. Approximately 25 million deaths occurred in Europe alone with many others occurring in Africa and Asia. Some villages were deserted with the few survivors fleeing and spreading the disease further. The great population loss brought economic changes based on increased social mobility as depopulation elsewhere eroded peasant obligations (already weakened) to remain on their traditional holdings.

Alternative explanations

Recently the scientists Susan Scott and Christopher Duncan from Liverpool University have proposed the theory that the Black Death might have been caused by an Ebola-like virus, not any bacteria. Their rationale is that this plague spread much faster and the incubation period was much shorter than in plagues caused by Yersinia pestis, it also took place in completely ratless areas like Iceland, it was transferred between humans (which happens rarely with Yersinia pestis), and some genes that determine immunity to Ebola-like viruses are much more widespread in Europe than in other parts of the world.

Moreover, what was previously considered to be final evidence for the Yersinia perstis theory, tooth pulp tissue taken from a 14th century plague cemetery in Montpellier containing Y. pestis DNA, was never confirmed in any other cemetery.

There are counter-arguments to this theory, however. Historical examples of pandemics of other diseases in populations not previously exposed, such as smallpox and tuberculosis amongst American Indians, show that because there is no inherited adaptation to the disease, its course in the first epidemic is faster and far more virulent than later epidemics amongst the descendents of survivors. The middle East and far East were affected equally badly (as the Rihla of Ibn Battuta testifies), so the prevalence of immunity genes specifically in Europeans is curious. Furthermore, the plague returned again and again and was recognised as the same disease through succeeding centuries into modern times when the Yersinia bacterium was identified.


  • Mark Derr: New Theories Link black Death to Ebola-Like Virus, The New York Times, Science Section, October 2, 2001.

See also: Great Plague