Mortuary cros from plague victim, 1348.

The plague is caused by infection with Yersinia Pestis, carried by fleas that infest rodents which then bite humans. The plague is thought to have originated from the Eastern provinces of China, and travelled along the well established Silk Road through the Middle East and the Eastern Mediterranean, before reaching southern Italy in 1347 and the rest of Europe soon after. Also known as the bubonic plague and the Black Death, it killed one third of the population of Europe. Outbreaks of the plague continued to occur in Europe until the 17th century.