Black Death

Infection and migration

The plague disease, generally thought to be caused by Yersinia pestis, is enzootic (commonly present) in populations of fleas carried by ground rodents, including marmots, in various areas including Central Asia, Kurdistan, Western Asia, Northern India and Uganda.[17] Nestorian graves dating to 1338–9 near Lake Issyk Kul in Kyrgizstan have inscriptions referring to plague and are thought by many epidemiologists to mark the outbreak of the epidemic, from which they could easily have spread to China and India.[18] In October 2010, medical geneticists confirmed that the plague originated in Yunnan, province in southwest China.[6] In China, the 13th century Mongol conquest caused a decline in farming and trading. However, economic recovery had been observed in the beginning of the 14th century. In the 1330s a high frequency of natural disasters and plagues led to widespread famine starting in 1331, with a deadly plague arriving soon after.[19] The 14th-century plague killed an estimated 25 million Chinese and other Asians during the 15 years before it entered Constantinople in 1347.[20] However, according to George Sussman, the first obvious medical description of plague in China dates to 1644.[21]

The disease may have travelled along the Silk Road with Mongol armies and traders or it could have come via ship.[22] By the end of 1346 reports of plague had reached the seaports of Europe: "India was depopulated, Tartary, Mesopotamia, Syria, Armenia were covered with dead bodies".[23]

Plague 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, taking the plague by ship into Sicily and the south of Europe, whence it spread north.[24] Whether or not this hypothesis is accurate, it is clear that several existing conditions such as war, famine, and weather contributed to the severity of the Black Death.