What the Black Death was
The Black Death was a devastating outbreak of plague that swept through Europe, the Middle East and North Africa in the middle of the fourteenth century. In Europe the main wave is usually dated to about 1347 to 1351, though the disease had been moving westward for some years before it reached Mediterranean ports. The name “Black Death” is much later than the events themselves. People at the time more often spoke of “the pestilence” or “the great mortality.” The word “black” probably came into common use long afterward, and historians do not agree on exactly why.
The disease behind it is now generally accepted to be plague, caused by the bacterium Yersinia pestis. For many years some scholars questioned this, but analysis of ancient DNA recovered from fourteenth-century burial sites has made the identification widely accepted. Plague normally lives in wild rodents and is carried between animals, and sometimes to people, by fleas.
The forms of the illness
Plague can take several forms, and medieval writers described symptoms that fit more than one of them.
- Bubonic plague causes painful swollen lymph nodes, called buboes, usually in the groin, armpit or neck, along with fever and weakness.
- Pneumonic plague infects the lungs and can pass directly from person to person through coughing.
- Septicemic plague enters the bloodstream and can kill very quickly.
Chroniclers wrote of swellings, fevers, spitting of blood and sudden death. Because their accounts were written by observers who did not understand the cause, they are valuable but should not be read as precise medical records.
How the disease spread so fast is still debated. The traditional picture of black rats and their fleas carrying plague from ship to ship and house to house has been challenged. Some researchers have argued that human fleas and lice, and person-to-person spread, may have mattered more in some places. The question is not fully settled.
When and where it struck
The outbreak is traditionally traced to the Black Sea region and Central Asia, from where it moved along the trade routes that connected the Mediterranean to the east. It reached Sicily and other Italian ports in late 1347, spread through Italy and southern France in 1348, crossed to England that same year, and moved on to Germany, Scandinavia and the Baltic over the following years. By the early 1350s it was reaching parts of Russia.
Not every place was hit equally. Some regions appear to have suffered terribly, while others seem to have been touched more lightly, and records for many areas are thin. Separate articles follow how the plague reached and moved across Europe in more detail.
How many died?
This is the question people ask first, and the honest answer is that nobody knows precisely. No government of the time counted the dead in any consistent way. Historians instead work from fragments: parish records, the replacement of priests, tax and rent rolls, wills, manorial court records and the number of tenancies that fell vacant. These sources survive unevenly and tend to cover better-documented places, such as parts of England and Italy.
Estimates for Europe as a whole are often given as somewhere between about one third and one half of the population, though some scholars argue for lower figures and others accept higher ones for particular regions. Contemporary chroniclers sometimes gave enormous numbers, but these were frequently exaggerations or guesses and are treated with caution. A fuller discussion of how scholars reason about the evidence is in the companion piece on plague mortality.
Why it hit so hard
Several conditions probably helped the disease. Europe had a large population by the early fourteenth century, and after earlier hardships such as the famines of the 1310s, many people may have been poorly nourished. Dense and crowded medieval towns, with limited sanitation by modern standards, allowed infection to spread. Busy trade and travel moved goods, and with them infected fleas and people, quickly between regions.
Medical understanding offered little defense. Physicians generally explained illness through humoral theory and through ideas about corrupted air, and the remedies they offered could not stop a bacterial infection. Some places did try isolating the sick and restricting travel, which are early forms of what we would call quarantine.
How people responded
Responses ranged from practical to desperate. Families tried to flee, though that sometimes carried the disease along. Physicians prescribed diets, herbs and bloodletting. Communities held processions and prayed. Some groups turned to extreme penance, and in several regions frightened communities turned on minorities, especially Jews, who were falsely accused of causing the disease. Church authorities condemned some of this violence, though they did not always succeed in stopping it.
Practical life was disrupted as well. Burying so many dead strained ordinary funeral customs, and in many places clergy and gravediggers were in short supply. Medieval hospitals and religious houses cared for the sick as best they could, and many of those who tended the ill died themselves.
Lasting effects
The long-term consequences are still discussed, and historians are careful about claiming too much. In many places the sudden loss of workers is thought to have made labor scarcer and wages higher, which strained the old relationships between lords and unfree peasants. Landowners and governments sometimes tried to hold wages down by law, with mixed success. Elsewhere the changes were more gradual, and some historians stress that the plague accelerated trends already under way rather than creating entirely new ones.
The plague also did not end in 1351. It returned in waves for centuries, often striking children and the young in later outbreaks. Over the same decades Europe was dealing with war, including the early phases of the Hundred Years War, and the disease was one pressure among many on the medieval economy. The Black Death is best understood not as a single moment but as the start of a long period of recurring plague, adjustment and change.
What remains uncertain
Several basic points are still open: the exact total of deaths, how much the numbers differed from region to region, how much pneumonic spread mattered compared with flea-borne spread, and how far the economic changes can be traced to the plague alone. Readers should treat any single confident figure, whether for deaths or for the share of the population lost, as an approximation.