In 1347, Siena, a flourishing, beautiful city-state on Tuscany hills, was a leading world power for its age. Just one year later, plague had already killed almost half of its inhabitants, changing its history forever. That did not happen only there: the impact of the Black Death – as the Middle Age epidemic was named – involved all Europe, with huge human, economic, political and cultural consequences. A typical, extreme, example of how infectious diseases can influence the course of history.