TED Case Studies

The Role of Trade in Transmitting the Black Death

CASE NAME: The Black Death


1. The Issue

Between 1339 and 1351 AD, a pandemic of plague traveled from China to Europe, known in Western history as The Black Death. Carried by rats and fleas along the Silk Road Caravan routes and Spice trading sea routes, the Black Death reached the Mediterranean Basin in 1347, and was rapidly carried throughout Europe from what was then the center of European trade. Eventually, even areas of European settlement as isolated as Viking settlements in Greenland would be ravaged by the plague. By the time these plagues had run their course in 1351, between 25 and 50% of the population of Europe was dead. An equally high toll was exacted from the populations of Arabia, North Africa, South Asia, and East Asia. This paper will examine the role of trade in the spread of the plague.

Note: Europe is a crucial focus to plague as a trade related issue for this reason. Since plague is not native to the European region, the relationship between Medieval trade and Medieval Europe's greatest ecological disaster become obvious. 2. Description The Black Death was actually a combination of three different types of plague: bubonic, pneumonic, and septicaemic, with bubonic being the most common. The bacteria which causes the diseases lives in the digestive tract of fleas, most frequently rat fleas. Plague bacteria can continue to survive in places like rat burrows (dark, moist environments) even after the plague has killed off all the rats in an infected group. Thus, the plague can lay dormant for a lengthy period of time until a new group of rodents moves into an infected burrow. Rats were extremely important to spreading the plague, but they were not the only means of dissemination. Through the spread of fleas among rodent populations, plague outbreaks can strike both urban and rural areas. Furthermore, the plague-bearing fleas could be transmitted to virtually any type of household or farm animal (1).

Bubonic Plague has an incubation period, from infection to the first symptoms, of approximately six days. The initial symptom is a blackish pustule forming over the point of the bite, followed by swollen lymph nodes near that bite. This is followed by subcutaneous hemorrhaging, which produces bruise-like purple blotches, called buboes, on the victim's skin. It is from this word, buboe, that the bubonic plague takes its name. The hemorrhaging causes an intoxication of the nervous system, which produces neurological and psychological disorders, including insomnia, delirium, and stupor (2). These disorders, particularly delirium, might be behind the bizarre danse macabre performed by plague victims that is described in medieval chronicles. Bubonic Plague is the least toxic of the three types, but still kills 50 to 60% of its victims (3).

Septicaemic plague is, like the bubonic plague, carried by insects. Its distinguishing feature is its rapidity - death occurs within a day of infection, even before buboes have had time to form. This form of the plague is the rarest rare, but is almost always fatal (4).

Pneumonic plague differs from the other two forms in that it can be spread from person to person. After a two to three day incubation period, victims suffer a sharp drop in body temperature, which is followed by sever coughing and discharge of a bloody sputum. This sputum contains the plague bacteria, making for an airborne transmission. As in bubonic plague, neurological and psychological disorders follow. Pneumonic plague is rarer than bubonic, but is fatal in over 95% of its victims (5).

None of these plagues are native to Europe. Plague bacteria normally resides in Central Asia, Yunan China, Arabia, East Africa, and limited areas of Iran and Libya. One reason for this is climactic. The weather in Northern Europe is hostile to the plague bearing fleas to such an extent that regular outbreaks would not be possible even in the summers, let alone the winters of 14th Century Europe (6). Their spread to Europe from these areas has always been through global commerce - trade which carried with it plague- bearing rats and fleas.

The first instance of a plague outbreak in Europe was Justinian's Plague, which raged from 541 to 544 AD, with sporadic lesser outbreaks of the plague lasting until the end of the Eighth Century. Outbreaks of Justinian's Plague almost invariably followed the same pattern. It is believed to have been carried down the Nile, from East Africa into the Mediterranean Basin. It rapidly spread along the trading routes from Egypt's main port, Alexandria, to Central and South Asia, Arabia, North Africa, and much of Southern Europe. Justinian's Plague was quite terrible - between years 541 and 542 about 40% of Constantinople, the central trading port of the Mediterranean world then, died of the plague. By the end of 544, it is estimated that 20 to 25% of the population of Europe south of the Alps had been killed by the plague. The spread of the plague into Northern and Central Europe was limited, probably by the lack of a significant trade infrastructure to the North in what was the ensuing Dark Ages (7).

By the 14th Century, things had changed. Due to technological innovations in agriculture, such as the three-field planting system, the population of Europe had risen to a level that it had not seen in a millennia, during the Roman Empire (8). This is despite the "Little Ice Age," a period of climactic deterioration and generally colder weather, which would not end until the mid-16th Century (9). A well-developed trade network in expensive luxury goods existed, carrying products by three main routes. The first was entirely overland, running from Northern China, through Central Asia, and then to the Black Sea. This was the famous "Silk Road." Spice trading ran along a route from South Asia to the Persian Gulf, and thence overland by caravan to the Levant. A second spice route ran by sea from South Asia to the Red Sea and Egypt (10).

From the Black Sea, the Levant, and Alexandria (still Egypt's main port), goods were picked up most often by Italian middlemen, who plying routes along the Mediterranean Basin, which was the nexus of European trade, delivered goods to Italy, Catalonia, and Southern France. By the 14th Century, there were also developed routes through the Straits of Gibraltar to England and Holland. From England and Holland, trade by sea extended into the Baltic, reaching lands as far away as Muscovy.

The great pandemic of plague, known in Europe as the Black Death, is thought to have begun in China in the early 1330s. Reliable chronicles tell of an outbreak of the plague in China, beginning in 1331. Sources in Latin, Arabic, and Chinese tell of numerous natural disasters such as floods and earthquakes. These events might have destroyed the habitats of the plague-bearing rodents, forcing them into contact with other rodent populations and thus spreading their fleas (11). By the 1350s, two-thirds of China's population lay dead (12).

Transmission of the Black Death Along Trading Routes

Major Trading Region Year of First Arrival
Central Asia
Volga River
Lower Eygpt
Southern Italy
Northern Italy
Northern Germany

From China, the plague is known to have been carried along the Silk Road into Central Asia, where there are records of outbreaks in 1339. Slowly, plague reached Sarai, on the Volga River, and the Crimea in 1345. From there it spread rapidly. By the next year, 1346, plague epidemics broke out in Astrakhan, Azerbaijan, and throughout the Caucasus. The northern and eastern shores of the Black Sea were ridden with plague, where the plague carrying fleas and rats were picked up in merchant ships and carried south, hiding in bulky crates and scurrying about ship (13).

In 1347, the plague struck Constantinople, no longer the center of Mediterranean trade, but still an important port. It also reached other important ports that year - Alexandria, Genoa, and ports in Sicily and Cyprus. From there it spread rapidly throughout the Mediterranean. By 1348 there were outbreaks in Cairo, Antioch, and much of southern Italy and Europe. Plague could move into the hinterland with only slightly more difficulty than traveling by sea, as urban rodents would share their infected fleas with their rural cousins, and sometimes infected livestock would be driven from a town into the countryside. Italy, its many mercantile city- states now the center of Mediterranean trade, suffered most heavily. Conservative estimates place the toll of the plague at one third of the populace, but many think it may have been as high as even one-half. By 1350, the plague had run its course through the Mediterranean Basin, carrying away between 35 to 40% of the population in that region. Following the sea lanes and rivers, it moved north (14).

Often, when a merchant ship full of dying and dead men came into port, the port authorities would order it quarantined, but this proved to be of little use. The quarantine was meant to keep sick sailors and traders from entering the town, not the disease bearing rats and fleas that would scurry down the ropes tying the ship to port.

The plague entered France, the most populace Kingdom of the 14th Century, primarily down routes such as the Rhone valley. The Black Death arrived in Paris in 1348, a city at with perhaps as many as 200,000 people living there. By the peak of the plague, reached in the months of November and December, Paris was losing as many as 800 people a day; 30% of the population of Normandy perished (15).

In 1349 it had reached Bergen, in Norway. Bergen was a member of the Hanseatic League, a confederation of Baltic trading towns, and a major commercial center. It was carried on a wool ship from London, the entire crew dead upon arrival. Plague was particularly severe in Scandinavia, perhaps because the cold weather caused pulmonary complications, and thus facilitated the deadly pneumonic plague. Plague deaths reached to between 45 and 55% of the population in Scandinavia. Yet even more grim is the transmission from Scandinavia to the Nordic settlements in Greenland. Greenland imported many of it supplies. Plague moved along the trade routes to Iceland, where it killed 60% of the populace, and then onto Greenland, reaching there probably in the winter of 1350. It annihilated the small population there. Chronicles tell of traders arriving in Greenland only to find villages deserted, with only the cattle roaming wild in them (16).

The Black Death is best documented in Britain, where it is believed to have arrived on Gascon ships to the port of Melcombe Regis, in 1348. Other outbreaks followed across southwest England. It reached London in the September of that year. London was the largest town of an overwhelmingly rural country, with a population of 50,000. It also suffered from extraordinarily poor sanitation. The plague ravaged London until the spring of 1350, killing between 35 to 40% of the populace. The port of Bristol also suffered 35-45% morbidity. Winchester may have reached a morbidity rate of 50%; there were so many deaths that High Street, the main urban road, was consecrated and used as a burial ground (17).

Ireland was stricken in 1349. The Black Death came through the passes in the Alps in to Germany, and across the Rhine from France and Holland. Hamburg, the second most important port in the Hanseatic League, two-thirds of the population died of plague. Nuremberg, an important hub in trans-Alpine overland trade, the plague eliminated 10% of the populace, despite Nuremburg's excellent public health system. Mortality in Germany was, on the whole, lower than elsewhere. Yet morbidity rates in Baltic ports were often as high as could be found elsewhere in Europe (18).

Eastern Europe was struck by the plague, but not as virulently as elsewhere in Europe. By 1351, when the plague was moving in that direction, along the rivers and through the Baltic, the epidemic was two and a half years old. By then, it is possible that the plague bacteria had mutated into a less virulent form. Geography also probably played a role. Bohemia, for example, is ringed on all sides but the east by mountains, and was not a major trading locale. Fewer rats lived there, and fewer still could have been imported. Neighboring Hungary lay on a plain, and was thus the habitat for many varieties of rodents. It also lay astride the Danube, and was hit much harder by the plague. Unfortunately, there are not reliable records as to the extent of the plague's morbidity in Eastern Europe (19).

By 1350 or 1351, the plague had finally reached the same region by which it entered Europe: Russia. By an ironic coincidence of geography, the trading routes in use did not run North across the steppes. Instead, it was carried into the Duchy of Muscovy through the Baltic ports and through Poland. As in Poland or Hungary, records of the death rates in Russia are unreliable. Yet native chronicles all agree that the Black Death was the worst epidemic in history (20).

This opinion is not limited to Europe. It is known that the plague also struck across the Moslem world. Evidence suggests that by 1349 one-third of the total population, and 40 to 50% of the urban populace of the Moslem world lay dead of the plague (21). Cairo, for example, lost one-third to two-fifths of its populace. The Plague reached Mecca, via the pilgrimage traffic (22). The Black Death ranks simply as the greatest ecological disaster of Medieval times, devastating human and certain animal populations across Eurasia and North Africa.

In Europe and the Middle East, local plague outbreaks would recur every few years until the 16th Century, keeping human populations in check and resulting in a long-term depopulation. It was not for two Centuries that Europe would return to the population level of the mid-14th Century. Ironically, this ecological disaster had some positive environmental effects. The depopulation caused the abandonment of much farm land, resulting in its return to the pastures or forests (23). The severe depopulation was a major contributing factor to many socio-economic changes in Europe, such as the decline of manorial feudalism.

Plague outbreaks continue to this day, even in Western countries with advanced medical and public health techniques. Plague-bearing rats returned to Britain in the early 20th Century in much the same way the arrived in the mid-14th Century: carried by merchant ships between 1896 and 1910, bubonic plague appeared in limited and sporadic outbreaks across Britain, but with the earliest cases being in ports Cardiff, Liverpool, Bristol, Hull, and London. Suffolk was struck by the pneumonic plague between 1910 and 1918. These outbreaks resulted in very little loss of life (24).

Other diseases are often geographically transmitted by trade and/or travel. The transmission of the global influenza epidemic during and after World War One is one example, carried by soldiers returning home from the unsanitary trenches of the Western Front. Filoviruses, such as Marburg and Ebola, are known to be transmitted out of Africa by the trade in medical research monkeys. HIV is thought to have spread throughout Central Africa by truck drivers sleeping with infected prostitutes along highway stops. Trade continues to have a strong connection with the spread of deadly diseases.

3. Related Cases:
BST Case
BST Case

4. Draft Author: Richard Thomas, May, 1997


5. Discourse and Status: Disagreement and Complete (Historical)

There are no historical indications of any international effort to deal with the Black Death in the 14th Century. Given the state of international relations at the time, this should not be surprising. Europe was still in deep in the feudal era during the 14th Century, with the focus of political power being the local Lord and the Manor. There were exceptions, particularly in the Mediterranean, but political perceptions of the time were strictly localized. It is doubtful that any 14th Century leaders even considered mounting an international effort to stop the progress of the plague, and even more doubtful that such an effort would have met any success, given the woeful state of medical knowledge at that time.

Modern historians and medical science are in general agreement about the causes of the plague, and the main means of dissemination - rats and fleas carried from port to port by merchant ships. Some debate remains over the true extent of the plague's morbidity. This is likely more due to the general unreliability and/or lack of Medieval records than anything else. There is even more disagreement on what the historical effects of the Black Death on European civilization.

Given the clear connection between trade and the spread of the Plague, however, and the connections between travel, trade and the spread of other diseases in the modern era, it is clear that this issue is still very relevant. More study should be given to the link between trade and disease, and more attention of stricter quarantine measures.

6. Forum and Scope: Many and Many

The Black Death was a pandemic, global in its proportions. It struck populations from China to Greenland. Yet each stricken community generally dealt with plague as if it were exclusively a local problem, even if it were aware that the neighboring shire, or even country was also afflicted by the plague. This was natural given the prohibitive nature of travel for the commoner, or even the upper classes at that time. The world outside of their village or town was something that most of the global populace was only dimly aware of and not very concerned with.

7. Decision Breadth: Many

The entire Old World trading system was effecting by the spread of the plague along its routes. From trading areas, it could easily spread inland as urban rodents spread plague-carrying fleas to their rural cousins.

Today, the Black Death is a matter of history, and is pursued by two different professions. One are European historians, who are interested primarily with the effects of the Plague on Europe's social and economic development. The other are those in medical sciences like Epidemiology, for whom the Black Plague is an important case study on Plague issues such as transmission, morbidity, outbreak causation, and other related issues.

8. Legal Standing: Law

Many local laws forbid or strictly controlled the presence of foreigners, particularly in Moslem areas.


9. Geographic Locations:

a. Domain: Global
b. Site: Global
c. Impact Global
10. Sub-National Factors: Yes

Given that the Black Death pre-dates the development of the modern nation-state, it would probably be more appropriate to view it in terms of a plague striking a panorama of local communities than a collection of states.

11. Type of Habitat: Many

The stretch of afflicted territory covers all possibilities excepting arctic.


12. Type of Measures: Regulatory Standard REGSTD

The Black Death had clear indirect and direct repercussions on trade. The direct would be of lesser impact - the quarantine of vessels carrying or suspected of carrying plague, given that trade was of central importance in plague dissemination. While such quarantines doubtless hindered the flow of trade, they were not of much use in stopping the spread of the plague, as they focused on the human crew, not the fleas and rats. A much more significant trade effect would be the indirect results, such as the effects on commerce resulting from sometimes as much as half of the labor supply or market demand dying from plague. An ecological disaster on the scale of the Black Plague has the necessary result of disrupting all human endeavors of scale, including economic.

13. Direct versus Indirect Impact: DIRECT

14. Relation of Trade to Resource Impact

a. Directly Related: No
b. Indirectly Related: Yes Plague
c. Not related: No
d. Process Related: Yes Health

15. Trade Product Identification: Many

16. Economic Data

17. Impact of Trade Restriction: VERY LOW

18. Industrial Sector: TRANSPORT

19. Exporter and Importer: MANY AND MANY

Virtually every country in Europe was involved in some from of import/export trade. However, the trade from Asia to Europe was mostly one-way, namely the export of luxury goods to Europe.


20. Environmental Problem Type: HEALTH

The Black Death was an ecological disaster on a global scale. The effects of the plague on human and certain animal populations from East Asia to as far west as Greenland were catastrophic.

21. Species

Name: Many, but particular attention to Humans
Type: Many
Diversity: Animal Life on a Global Scale

Plague bacteria are known to have debilitating and often lethal effects on a wide variety of animal life. For example, the flea- carrying rats were often observed to die, and it is known today that it was the Plague that was killing them. However, Medieval chroniclers understandably did not pay close attention to the probable effects of the plague on animals, so the extent of any damage the plague may have caused in animal populations cannot be known.

22. Resource Impact: LOW AND PRODUCT

The impact of the plague was high not on resources themselves, but on their exploitation due to the steep decline in available labor. The only direct effect on resources would be limited to the deaths of livestock and the disrepair of agricultural land caused by abandonment.

23. Urgency of Problem: LOW

The Black Plague does serve as a useful lesson on the dangers of transferring potentially biohazardous materials over long distances.

24. Substitutes: NO

25. Culture: YES

The Black Plague is thought by historians to have a major impact on the socio-economic development of Europe. The severe depopulation has been thought to either have contributed to or solely resulted in the decline of manorial feudalism, the rise of a money economy, wage labor, spurred technological development, and numerous other effects. That the Black Plague caused changes in the development of Europe is not disputed by historians, only how much change.

26. Human Rights: NO

27. Trans-Boundary Issues: NO



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1) Gottfried, Robert. The Black Death: Natural and Human Disaster in Medieval Europe. New York, Free Press (1983): p 6-7.

2) Twigg, Graham. The Black Death: A Biological Reappraisal. London, Bastford Academic and Educational, (1984): p 7-19.

3) Gottfried, p 8.

4) Gottfried, p 8.

5) Gottfried, p 8.

6) Twigg, p 123.

7) Gottfried, p 9.

8) Gottfried, p 11-12

. 9) Gottfried, p 35.

10) Twigg, p 118.

11) Gottfried, p 35.

12) Dols, Micheal. The Black Death in the Middle East. New Jersey, Princeton UP (1977): p 39.

13) Gottfried, p 36-37.

14) Gottfried, p 37-49.

15) Gottfried, p 54-55.

16) Gottfried, p 57-58.

17) Gottfried, p 59, 63-64.

18) Gottfried, p 67-69.

19) Gottfried, p 75.

20) Gottfried, p 76.

21) Dols, p 63, 215.

22) Gottfried, p 33, 245.

23) Gottfried, p 134-135.

24) Twigg, p 147-161.


Dols, Micheal. The Black Death in the Middle East. New Jersey, Princeton UP(1977).

Gottfried, Robert. The Black Death: Natural and Human Disaster in Medieval Europe, New York, Free Press (1983).

Gasquet, Franics Adian, Cardinal. The Black Death of 1348 and 1349. London, G. Bell (1908).

Twigg, Graham. The Black Death: A Biological Reappraisal. London, Bastford Academic and Educational (1984).

Ziegler, Philip. The Black Death. New York, John Day Co. (1969).