After reading the primary source, explain the possible causes of the Black Death. Students then observe a diagram of how the Black Death spread from a flea to humans. Check student understanding by having students drag to show the steps of how the disease spread in the correct order. Next, students view a map depicting the trade routes from China to Europe. They can choose a route and drag the ship to move from China to Europe. Explain that at the time, people had many incorrect theories about the cause of the Black Death, including earthquakes and even punishment from God. Next, students learn about the symptoms and how the disease progressed from a fever to the death of a victim. Explain how people in the Middle Ages did not understand diseases the way we do today. Doctors did not know how to stop it and so they had several unsuccessful ideas for cures including sitting by a fire and placing a toad on open sores.