The Black Death was one of the most devastating pandemics in human history, resulting in the deaths of an estimated 75 to 200 million people in Eurasia and peaking in Europe from 1346 to 1353. Its migration followed the sea and land trading routes of the medieval world. This migration has been studied for centuries as an example of how the spread of contagious diseases is impacted by human society and economics.
The disease is caused by Yersinia pestis, which is enzootic (commonly present) in populations of ground rodents in Central Asia. Morelli et al. (2010) reported the origin of the plague bacillus to be in China. An older theory places the first cases in the steppes of Central Asia, and others, such as the historian Michael W. Dols, argue that the historical evidence concerning epidemics in the Mediterranean and specifically the Plague of Justinian point to a probability that the Black Death originated in Central Asia (not Africa - Asia), where it then became entrenched among the rodent population.
Nevertheless, from Central Asia it was carried east and west along the Silk Road, by Mongol armies and traders making use of the opportunities of free passage within the Mongol Empire offered by the Pax Mongolica. It was reportedly first introduced to Europe at the trading city of Caffa in the Crimea in 1347. After a protracted siege, during which the Mongol army under Jani Beg was suffering the disease, they catapulted the infected corpses over the city walls to infect the inhabitants. The Genoese traders fled, bringing the plague by ship into Sicily and the south of Europe, whence it spread.
Regardless of its origin, it is clear that several preexisting conditions such as war, famine, and weather contributed to the severity of the Black Death. In China, the 13th century Mongol conquest disrupted farming and trading, and led to widespread famine. The population dropped from approximately 120 to 60 million. The 14th century plague is estimated to have killed 1/3 of the population of China.
In Europe, the Medieval Warm Period ended sometime towards the end of the 13th century, bringing harsher winters and reduced harvests. In the years 1315 to 1317 a catastrophic famine, known as the Great Famine, struck much of North-West Europe. The famine came about as the result of a large population growth in the previous centuries, with the result that, in the early 14th century the population began to exceed the number that could be sustained by productive capacity of the land and farmers.
In Northern Europe, new technological innovations such as the heavy plough and the three-field system were not as effective in clearing new fields for harvest as they were in the Mediterranean because the north had poor, clay-like soil. Food shortages and skyrocketing prices were a fact of life for as much as a century before the plague. Wheat, oats, hay, and consequently livestock, were all in short supply, and their scarcity resulted in hunger and malnutrition. The result was a mounting human vulnerability to disease, due to weakened immune systems.
The European economy entered a vicious circle in which hunger and chronic, low-level debilitating disease reduced the productivity of labourers, and so the grain output was reduced, causing grain prices to increase. This situation was worsened when landowners and monarchs like Edward III of England (r. 1327–1377) and Philip VI of France (r. 1328–1350), out of a fear that their comparatively high standard of living would decline, raised the fines and rents of their tenants. Standards of living then fell drastically, diets grew more limited, and Europeans as a whole experienced more health problems.
Heavy rains in autumn 1314 began several years of cold and wet winters. The already weak harvests of the north suffered and the seven-year famine ensued. The Great Famine was the worst in European history, reducing the population by at least ten percent. Records recreated from dendrochronological studies show a hiatus in building construction during the period, as well as a deterioration in climate.
This was the economic and social situation in which the predictor of the coming disaster, a typhoid (Infected Water) epidemic, emerged. Many thousands died in populated urban centres, most significantly Ypres. In 1318 a pestilence of unknown origin, sometimes identified as anthrax, targeted the animals of Europe, notably sheep and cattle, further reducing the food supply and income of the peasantry.
The scenario that would place the first outbreak in central Asia agrees with the first reports of outbreaks in China in the early 1330s. The plague struck the Chinese province of Hubei in 1334. On the heels of the European epidemic, a more widespread disaster occurred in China during 1353–1354. Chinese accounts of this wave of the disease record a spread to eight distinct areas: Hubei, Jiangxi, Shanxi, Hunan, Guangdong, Guangxi, Henan, and Suiyuan, throughout the Mongol and Chinese empires. Historian William McNeill noted that voluminous Chinese records on disease and social disruption survive from this period, but no one has studied these sources in depth.
It is probable that the Mongols and merchant caravans inadvertently brought the plague from central Asia to the Middle East and Europe. The plague was reported in the trading cities of Constantinople and Trebizond in 1344.
In October 1347, a fleet of Genoese trading ships fleeing Caffa reached the port of Messina in Sicily. By the time the fleet reached Messina, all the crew members were either infected or dead. It is presumed that the ships also carried infected rats and/or fleas. Some ships were found grounded on shorelines, with no one aboard remaining alive.
From Italy the disease spread northwest across Europe, striking France, the Crown of Aragon, the Crown of Castile, Portugal and England by June 1348, then turned and spread east through Germany and Scandinavia from 1348 to 1350. It was introduced in Norway in 1349 when a ship landed at Askøy, then proceeded to spread to Bjørgvin (modern Bergen). Finally it spread to north-western Russia in 1351; however, the plague largely spared some parts of Europe, including the Kingdom of Poland, isolated parts of Belgium and the Netherlands, Milan and the modern-day France-Spain border.
At Siena, Agnolo di Tura wrote:
"They died by the hundreds, both day and night, and all were thrown in ... ditches and covered with earth. And as soon as those ditches were filled, more were dug. And I, Agnolo di Tura … buried my five children with my own hands … And so many died that all believed it was the end of the world."
The plague struck various countries in the Middle East during the pandemic, leading to serious depopulation and permanent change in both economic and social structures. As it spread to western Europe, the disease also entered the region from southern Russia. By autumn 1347, the plague reached Alexandria in Egypt, probably through the port's trade with Constantinople, and ports on the Black Sea. During 1348, the disease traveled eastward to Gaza, and north along the eastern coast to cities in Lebanon, Syria, and Palestine, including Ashkelon, Acre, Jerusalem, Sidon, Damascus, Homs, and Aleppo. In 1348–49, the disease reached Antioch. The city's residents fled to the north, most of them dying during the journey, but the infection had been spread to the people of Asia Minor.
Mecca became infected in 1349. During the same year, records show the city of Mawsil (Mosul) suffered a massive epidemic, and the city of Baghdad experienced a second round of the disease. In 1351, Yemen experienced an outbreak of the plague. This coincided with the return of King Mujahid of Yemen from imprisonment in Cairo. His party may have brought the disease with them from Egypt.
In England, in the absence of census figures, historians propose a range of pre-incident population figures from as high as 7 million to as low as 4 million in 1300, and a post-incident population figure as low as 2 million. By the end of 1350 the Black Death had subsided, but it never really died out in England over the next few hundred years: there were further outbreaks in 1361–62, 1369, 1379–83, 1389–93, and throughout the first half of the 15th century. The plague often killed 10% of a community in less than a year—in the worst epidemics, such as at Norwich in 1579 and Newcastle in 1636, as many as 30 or 40%. The most general outbreaks in Tudor and Stuart England, all coinciding with years of plague in Germany and the Low Countries, seem to have begun in 1498, 1535, 1543, 1563, 1589, 1603, 1625, and 1636.
The plague repeatedly returned to haunt Europe and the Mediterranean throughout the 14th to 18th centuries, and still occurs in isolated cases today.
The plague of 1575–77 claimed some 50,000 victims in Venice. In 1634, an outbreak of plague killed 15,000 Munich residents. Late outbreaks in central Europe include the Italian Plague of 1629–1631, which is associated with troop movements during the Thirty Years' War, and the Great Plague of Vienna in 1679. About 200,000 people in Moscow died of the disease from 1654 to 1656. Oslo was last ravaged in 1654. In 1656 the plague killed about half of Naples' 300,000 inhabitants. Amsterdam was ravaged in 1663–1664, with a mortality given as 50,000.
A plague epidemic that followed the Great Northern War (1700–1721, Sweden v. Russia and allies) wiped out almost 1/3 of the population in the region. An estimated one-third of East Prussia's population died in the plague of 1709–1711. The plague of 1710 killed two-thirds of the inhabitants of Helsinki. An outbreak of plague between 1710 and 1711 claimed a third of Stockholm’s population.
During the Great Plague of 1738, the epidemic struck again, this time in Eastern Europe, spreading from Ukraine to the Adriatic Sea, then onwards by ship to infect some in Tunisia. The destruction in several cities in what is now Romania (such as Timişoara) was formidable, claiming tens of thousands of lives.