From the east to the Mediterranean
The plague that reached Europe in the 1340s did not appear from nowhere. Evidence from the time and from modern genetic research suggests it came out of Central Asia or the lands around the Black Sea and moved along the same overland and sea routes that carried silk, spices and other goods. The details of the earliest stages are uncertain, and historians treat the story as a broad outline rather than a precise itinerary.
A well-known tradition places an important step at Caffa, a trading town on the Crimean coast held by merchants from Genoa. According to a chronicler writing in Italy, a Mongol army besieging the town was struck by plague and catapulted infected bodies over the walls. Historians doubt that this account is literally true, since it comes from a secondhand source and plague does not require such a mechanism, but most agree that the Black Sea ports were an early channel by which the disease reached Mediterranean shipping.
Sicily and the Italian ports
The first clearly recorded arrivals in Europe came in the fall of 1347. Traditionally, a small fleet of galleys put in at Messina in Sicily with sick and dying crew members, and the disease spread through the town and island within weeks. Whether this account holds in every detail is uncertain, but plague certainly appeared in Sicily around that time.
From there, Mediterranean sea traffic did the rest. Italian merchant cities such as Genoa and Venice were closely tied into eastern commerce, so it is not surprising that they were affected early. Italy suffered in 1348, and the city of Florence, whose experience was described in detail by the writer Giovanni Boccaccio, became one of the most famous examples. Some ports tried to turn away ships, with limited success.
Southern France and Iberia
Marseille and other ports on the southern coast of France were infected around the turn of 1347 to 1348. From there the disease moved up the Rhône valley and across the south. The papal court at Avignon was badly hit in the spring of 1348. It also spread into the Iberian peninsula, with the Crown of Aragon affected early and Castile following. Spread along rivers and roads meant that inland towns were often infected a few weeks or months after nearby ports.
Northern France, Britain and Ireland
In 1348 the disease reached Paris and the northern French cities. In the same year it crossed the Channel. The usual tradition places its arrival in England at a port on the south coast, in Dorset, in the summer of 1348, and from there it moved to Bristol, London and beyond. Peak mortality in much of England is usually dated to 1349. Wales, Scotland and Ireland were affected over the same period or shortly after, with the dates and severity varying by locality. Records in these regions are patchy, so the sequence is partly inferred.
Germany, Scandinavia and the Baltic
Plague moved north and east through German lands in 1349 and 1350. One often-told story has an English ship bringing the disease to Norway in 1349, which may be true in outline, but the details are traditional. From Norway, Sweden and Denmark were affected. Baltic ports, many of them part of the Hanseatic League’s trade network, were hit as the plague moved along maritime links. By the early 1350s the epidemic was reaching Poland and Russia, where it appears in the chronicles of cities like Novgorod and Pskov.
Regional differences
The advance was not a smooth wave. Some areas seem to have been hit unusually lightly, such as parts of Bohemia and Poland according to some historians, while others, including many Italian and French cities, appear to have suffered severely. The reasons for these differences are debated. Possible factors include population density, local trade patterns, climate, the timing of the arrival, and simple chance. Part of the apparent variation may also be a result of the records: places with good surviving archives look more thoroughly documented than they were compared with places with few records.
Why trade routes mattered
The pattern of arrival, ports first and then inland along rivers and highways, fits the picture of a disease carried by people and goods. Ships were a good vehicle: they carried infected fleas, rodents and passengers, and a voyage could arrive before symptoms had shown. Towns with heavy long-distance trade tended to be among the earliest affected. But the disease could also spread within a locality by short, local movement, such as markets, pilgrimages and funerals.
Winter slowed the spread in some regions, and in many places the epidemic seems to have peaked in the warmer months. Even so, the disease spread across the whole continent in about four to five years, which was a rapid pace for medieval travel.
What the evidence can and cannot show
The tidy sequence of dates is based on chronicles, official records and later tradition. Some dates are firm, others are best guesses. Dates for the arrival of the plague in a given town are often drawn from a single source. Readers should treat the order of events as a general guide. The broad picture, a Mediterranean entry in 1347 followed by sweeps north and east, is well established.