The Spread of Black Death


“They died in heaps and were buried in heaps.”

Daniel Defoe in England in 1665


          It is extremely rare for a pandemic to occur.  The conditions necessary for this type of global event to strike are severe.  Some of the pre-existing conditions necessary for this occurrence include war, famine, weather and interactions between people.  The civil war in China during the 13th and 14th centuries led to episodes of widespread famine.  Also, at the end of the 13th century and into the first half of the 14th century, disastrous weather had severe implications worldwide.  This so-called “Little Ice Age”, shifted the reservoir downward into the direct path of the Asian trade routes (TED 2).  These trade routes came in contact the Yersinia pestis as luxury items such as silk and spices were brought from Asia to Europe.  Also, The Great Famine struck all of Northern Europe in the 14th century, resulting in hunger and malnutrition.  The result was a mounting vulnerability to disease due to weakened immune systems.  A typhoid epidemic in 1318 became the predictor of the upcoming disaster.  In addition to these situations, it is necessary that the host population for the vector be stressed.  This usually is the result of a disease state or famine in the host which results in fewer sources of blood for the vector, so they seek other hosts.  Therefore, the infection transfers from the rat host to human hosts.


Figure 1(The spread of the bubonic plague from east Asia to Europe in the mid to late 14th century,


          Current evidence suggests that the Black Death spread from China in 1334 to Europe, primarily along trade routes (TED 2).  This occurred both over land with merchant caravans, as well as at sea along sea trade routes.  Evidence supports the transmission along sea routes by the observation that large active port cities had the highest infection and mortality rates.  By 1347, the outbreak had spread into Europe.  From Italy, the disease spread northwest across Europe inflicting the inhabitants of France, Spain, Portugal, and England by 1348.  Following this pandemic, there were isolated incidences of epidemics that occurred over the next two centuries.  It is estimated that the original Black Death pandemic claimed 25 million lives in Europe alone.



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