Black Death is created, allegedly, on March 20th, 1345.
Plague is a bacterial infection found mainly in rodents and their fleas. But via those fleas it can sometimes leap to humans. When it does, the outcome can be horrific, making plague outbreaks the most notorious disease episodes in history.
All the citizens did little else except to carry dead bodies to be buried […] At every church they dug deep pits down to the water-table; and thus those who were poor who died during the night were bundled up quickly and thrown into the pit. In the morning when a large number of bodies were found in the pit, they took some earth and shovelled it down on top of them; and later others were placed on top of them and then another layer of earth, just as one makes lasagne with layers of pasta and cheese. (As related by a Florentine chronicler.)
Most infamous of all was the medieval pandemic that swept through Asia and Europe. It reached Europe in the late 1340s, killing an estimated 25 million people. And, mind you, there wasn’t quite as many Europeans in those times as there are now — merely 70 million.
The chronicler Agnolo di Tura ‘the Fat’ relates from his Tuscan home town that
… in many places in Siena great pits were dug and piled deep with the multitude of dead […] And there were also those who were so sparsely covered with earth that the dogs dragged them forth and devoured many bodies throughout the city.
The Black Death lingered on for centuries, particularly in cities. Outbreaks included the Great Plague of London (1665-66), in which one in five residents died.
The cause of plague wasn’t discovered until the most recent global outbreak, which started in China in 1855 and didn’t officially end until 1959. The first breakthrough came in Hong Kong in 1894 when researchers isolated the rod-shaped bacillus responsible—Yersinia pestis. A few years later, in China, doctors noticed that rats showed very similar plague symptoms to people, and that human victims often had fleabites.