The region that was hit the hardest by the bubonic plague in the 1300's was the Mediterranean region.
Big portions of Europe had big losses when this disease came to the European soil, but the Mediterranean region, on European, Asian, and African soil, was hit the hardest and had the biggest losses in human lives. The body didn't had a defense system for this disease nor do the medics of the period had a solution for it, so once someone got it, it meant that the person is destined to die in a matter of days.