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The plague disease, or Black Death, caused by ''Yersinia pestis'', is enzootic (commonly present) in populations of ground rodents in Central Asia. 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 Africa and spread to Central Asia, where it then became entrenched among the rodent population.〔Michael W. Dols, "The Second Plague Pandemic and Its Recurrences in the Middle East: 1347–1894" ''Journal of the Economic Social History of the Orient''vol. 22 no. 2 (May 1979), 170–171.〕 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. Whether or not this hypothesis is accurate, 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.〔Ping-ti Ho, "An Estimate of the Total Population of Sung-Chin China", in ''Études Song'', Series 1, No 1, (1970) pp. 33–53.〕 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.〔Bennett and Hollister, ''Medieval Europe, p. 327〕 Standards of living then fell drastically, diets grew more limited, and Europeans as a whole experienced more health problems. In the autumn of 1314, heavy rains began to fall, which led to 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. ==Asian outbreak== 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,〔Suiyuan was a historical Chinese province that now forms part of Hebei and Inner Mongolia.〕 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.〔McNeill, William H. (1976). ''Plagues and People''. New York: Anchor Books. ISBN 0-385-12122-9.〕 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Black Death migration」の詳細全文を読む スポンサード リンク
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