What factors may have contributed to the loss in population in Venice, Rome, and London between 1300 and 1400?

the mongolian invasion of china and central asia resulted in a disruption of the silk road as the chinese garrisons lost support from the chinese kingdoms which fell under the mongols. however, as the mongols established a formal dynasty in china, the successors of genghis khan restored the garrisons along the silk road allowing the safe travel caravans again.

i think iowa because you committed the crime there