Trade Ships had lots of rats on them. These rats are infected because of fleas. The fleas are infected from other countries, which is where the Plague started.
The infected rats were everywhere! Therefore people came into contact with them and got infected thereselves!
Infected people came into contact with even more people, and most of the population got infected and died.
Symptoms include fever, headache, chills, and other stuff. Although the most notable effect is swollen areas around the body that develop black spots called buboes. Some can be as big as an egg
There are two types of plague. The Bubonic and The Pheunomic. The bubonic is more common and is n the bloodstream of rats. The Pneumonic is the more deadly and rare one. It was gotten when an infected person sneezed.
Some people would try to cure the plague by getting the plague doctor to poke the swellings with a long stick. They had to pop all of them. There were multiple other treatments but this was the preferred one.