The Symptoms of the Black Death

Engraving of Florence During a 14th-Century Plague
Engraving of Florence During a 14th-Century Plague. Bettman / Getty Images

The Black Death is a plague which killed millions of people. In one particularly destructive explosion, over a third of the whole European population might have died in a few years in the mid 14th century, a process which changed history, birthing, among other things, the start of the modern age and the Renaissance. For a history of the Black Death in Europe, see our page here. This is an explanation of what happens when someone contracts it. You really have to hope you never do!

How you get the Black Death

Despite plenty of people trying to claim other things, the evidence comfortably points to The Black Death being Bubonic Plague, caused by the bacterium Yersinia Pestis . A human being usually receives this by being bitten by a flea which has ingested the disease from the blood of a house rat. The infected flea has had its system blocked by the disease, and remains hungry, regurgitating older infected blood into a human before drinking new blood, spreading infection. The rat’s flea doesn’t usually target humans, but seeks them out as new hosts once their colony of rats die off from the plague; other animals could also be affected. Plague carrying fleas didn’t have to come straight from a rat, as the fleas could survive for several weeks in bundles of cloth and other items humans conveniently came into contact with. On rarer occasions, a human could receive the disease from infected droplets which had been sneezed or coughed out into the air from a sufferer of a variation called Pneumonic Plague.

Even rarer still was infection from a cut or sore.


Once bitten, a victim experienced symptoms like headaches, chills, high temperatures and extreme tiredness. They might have nausea and pain throughout their body. Within several days the bacteria had begun affecting the body’s lymph nodes, and these swelled up into painful large lumps called ‘buboes’ (from which the disease takes its popular name: Bubonic Plague). Usually those nodes closest to the initial bite were first, which normally meant in the groin, but those under the arms and in the neck were also affected. They could reach the size of an egg. Suffering great pain, you could then die, roughly a week after you were first bitten.

From the lymph nodes the plague could spread and internal bleeding would begin. The sufferer would expel blood in their waste, and black spots could appear all over the body. Sufferers with the spots almost invariably died, and this is noted in the chronicles of the day. The disease could spread to the lungs, giving the victim Pneumonic Plague, or into the bloodstream, giving Septicaemic Plague, which killed you before the buboes appeared. Some people did recover from the Black Death – Benedictow gives a figure of 20% - but contrary to the beliefs of some survivors they did not gain an automatic immunity.

Medieval Reaction

Medieval doctors identified numerous symptoms of the plague, many of which correlate with modern knowledge. The process of the illness through its stages wasn’t fully understood by medieval and early modern doctors, and some interpreted the buboes as signs the body was trying to vent foul liquids. They then attempted to relieve the illness by lancing the buboes. A punishment from God was seen at the frequent underlying course, although quite how and why God was inflicting this was heatedly discussed. The situation wasn't one of total scientific blindness, as Europe has always been blessed with proto-scientists, but it was confused and unable to react like modern science. Even so, you can still see this confusion exist today when it comes to popular understanding of illness.