Scholars often dispute the origin of the bubonic plague. One legend holds out that the plague broke out in the Tarter army under Khan Djani-Beg that was besieging the city of Caffa in the Crimea. The Khan ordered the heads of Tarter victims hurled into Caffa to infect the defenders. Others say that the plague broke out in China or central Asia around 1331, and during the next fifteen years, merchants and soldiers carried it over the caravan routes until it reached the Crimea in 1346.
Some scholars believe that the plague was endemic is southern Russia. Either way, the plague had easy access to the Mediterranean lands and Western Europe. It spread very rapidly in Europe because Genoese ships brought the plague to Messina, which then spread to Sicily. By June of 1348, Venice, Genoa, Pisa, Florence, Tuscany, southern Germany, Languedoc, Spain, and England were all infected.