Middle Eastern traders brought spices and rats carrying fleas with the bubonic plague to a city of 10 million people. If each flea bit one person per hour, the document calculates that 48,000 people would be infected within two days as the plague spread rapidly through the population. The plague, known as the Black Death, spread quickly throughout Europe in the late Middle Ages after traders opened routes between Asia, the Middle East and Europe, carrying infected rats. It resulted in approximately 38 million deaths between 1347-1351.