The infected rats came on ships that pulled into the port at Messina.
The sickness affected cows, sheep, goats, pigs, and chickens, as well as people.
This plague spread through the air or from the bite of infected fleas and rats. These pests could be found almost everywhere in Medieval Europe.
The disease was also very efficient, people who were perfectly healthy when they went to bed at night could be dead by morning.
First poeple would get swellings on the groin or under the armpits; then they would have other symptoms like a fever, chills, vomiting, diarrhea, terriblie aches and pains, then death.
Healthy people did what they could to avoid the sick; doctors refused to see patients, priests refused to administer las rites, and shopkeepers closed their stores; many people fled to the countrysides but they still could not escape the disease.