Second plague pandemic

The second plague pandemic is a major series of epidemics of the plague that started with the Black Death, which reached mainland Europe in 1348 and killed up to a third of the population in the next four years. Although it died out in most places, it became epizootic and recurred regularly until the nineteenth century. A series of major plagues occurred in the late 17th century and it recurred in some places until the 19th. After this a new strain of the bacterium appeared as the third pandemic.

Plague is caused by the bacterium Yersinia pestis which exists in the fleas of several species in the wild and particularly rats in human society. In an outbreak it may kill all its immediate hosts and thus die out, but remain active in other hosts which it does not kill and thereby cause a new outbreak years or decades later. It has several means of transmission and infection, including rats carried on board ships or vehicles, fleas hidden in grain, and in its more virulent forms is transmitted by blood and sputum directly between humans.

There have been three major outbreaks of plague. The Plague of Justinian in the 6th and 7th centuries is the first known attack on record, and marks the first firmly recorded pattern of bubonic plague. From historical descriptions, as much as 40% of the population of Constantinople died from the plague. Modern estimates suggest half of Europe's population died as a result of the plague before it disappeared in the 700s. After 750, major epidemic diseases did not appear again in Europe until the Black Death of the 14th century.

The Second pandemic originated in or near China and spread by way of the Silk Road or by ship. It may have reduced world population from an estimated 450 million down to 350–375 million by the year 1400.

The plague returned at intervals with varying virulence and mortality until the early 19th century. In England, for example, the plague returned in 1360–63 killing 20% of Londoners and in 1369 killing 10–15%. In the 17th-century outbreaks were a series of "great plagues": the Great Plague of Seville (1647–52); the Great Plague of London (1665–66); and the Great Plague of Vienna (1679). In its virulent form, after the Great Plague of Marseille in 1720–22, the Great Plague of 1738 (which hit Eastern Europe), and the Russian plague of 1770–1772, it seems to have gradually disappeared from Europe though lingering in Egypt and the Middle East. By the early 19th century, the threat of plague had diminished, but it was quickly replaced by a new disease. The Asiatic cholera was the first of several cholera pandemics to sweep through Asia and Europe during the 19th and 20th centuries.

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