* Trade and travel: The Black Death was spread through trade and travel, as people who were infected with the disease traveled from one place to another. This was especially common in port cities, where merchants and sailors would come into contact with people from all over the world.
* Fleas and rats: The Black Death was spread by fleas and rats. Fleas would feed on rats that were infected with the disease, and then they would transmit the disease to humans when they bit them.
* Poor sanitation: Poor sanitation conditions made it easier for the Black Death to spread. There was a lack of clean water, and people often lived in close quarters, which made it easy for the disease to spread from person to person.
* Lack of immunity: Most Europeans had no immunity to the Black Death, as it was a new disease. This made it easier for the disease to spread and cause widespread death.