Where do you predict Yersinia pestis would diffuse from Kaffa?

Yersinia pestis is known as the causative agent of plague. Plague is a disease which has vectors such as rodents and fleas. They are transmitted to man when the fleas who have the plague bite man.

It is caused by bacteria and can be transmitted through saliva droplets which makes ships the place Yersinia pestis would more likely diffuse from Kaffa. The ship is usually packed with lots of people from different regions and parts of the world on trading businesses.