The Black Death (more recently known as the Black Plague) was a devastating pandemic that first struck Europe in the mid-14th century (1347–1350), when it was estimated to have killed about a third of Europe's population. A series of plague epidemics also occurred in large portions of Asia and the Middle East during the same period, which indicates this outbreak was actually a world wide pandemic. The same disease is thought to have returned to Europe every generation with varying degrees of intensity and fatality until the 1700s. Notable late outbreaks include the Italian Plague of 1629-1631, the Great Plague of London (1664–65), and the Great Plague of Vienna (1679).
The result of the plague was not just a massive decline in population. It irrevocably changed Europe's social structure, was a disastrous blow to Europe's predominant organized religion, the Roman Catholic Church, caused widespread persecutions of minorities like Jews and lepers, and created a general mood of morbidity which influenced people to live for the moment, unsure of their daily survival.
The initial 14th-century European event was called the "Great Mortality" by contemporary writers and, with later outbreaks, became known as the "Black" Death because of a striking symptom of the disease, called acral necrosis, in which sufferers' skin would blacken due to subdermal hemorrhages. Historical records attribute the Black Death to an outbreak of bubonic plague, an epidemic of the bacterium Yersinia pestis spread by fleas with the help of animals like the black rat (Rattus rattus), although today's experts debate both the microbiological culprit and mode of transmission.
Information about the death toll varies widely by area and from source to source. Approximately 25 million deaths occurred in Europe alone, with many others occurring in northern Africa, the Middle East and Asia.
Estimates of the demographic impact of plague in Asia are based on both population figures during this time and estimates of the disease's toll on population centers. The initial outbreak of plague in the Chinese province of Hubei in 1334 claimed up to 90 percent of the population, an estimated five million people. During 1353–54, outbreaks in eight distinct areas throughout the Mongol/Chinese empires may have caused the death of two-thirds of China's population, often yielding an estimate of 25 million deaths.
It is estimated that between one-third and one-half of the European population died from the outbreak between 1348 and 1350. As many as 25% of all villages were depopulated, mostly the smaller communities, as the few survivors fled to larger towns and cities. The Black Death hit the culture of towns and cities disproportionately hard; some rural areas, for example, Eastern Poland and Lithuania, were so isolated that the plague made little progress. Cities were the worst off because of the population densities and close living quarters making disease transmission easier.