Missed this last week from Livescience, from its "World Chainging Events" series. The plague killed as much as 1/3 of Europe, and an estimated 75 million died as a result of the disease. One theory holds the impact of the disease was magnified by the medieval "Little Ice Age", where global temperature levels dropped by as much as 4 degrees Fahrenheit. Both people and the rats carrying the disease huddled for warmth indoors, greatly aiding the spread of the plague.
"Following very precisely the medieval trade routes from China, through Central Asia and Turkey, the plague finally reached Italy in 1347 aboard a merchant ship whose crew had all already died or been infected by the time it reached port. Densely populated Europe, which had seen a recent growth in the population of its cities, was a tinderbox for the disease.
The Black Death ravaged the continent for three years before it continued on into Russia, killing one-third to one-half of the entire population in ghastly fashion.
The plague killed indiscriminately – young and old, rich and poor – but especially in the cities and among groups who had close contact with the sick. Entire monasteries filled with friars were wiped out and Europe lost most of its doctors. In the countryside, whole villages were abandoned. The disease reached even the isolated outposts of Greenland and Iceland, leaving only wild cattle roaming free without any farmers, according to chroniclers who visited years later."
The impact of the disease included better working conditions for peasants due to labor shortages, an increase in skepticism of the Catholic Church, and the scapegoating of European Jews, with a number of upleasant incidents, to say the least. Many Jews fled into Eastern Europe from other areas. World population levels took centuries to recover.