What were common diseases?

* Bubonic plague: Also known as the Black Death, this highly contagious disease was caused by the bacteria Yersinia pestis. It was spread by fleas that lived on rats and other rodents. The plague caused fever, chills, and swollen lymph nodes (buboes). It was often fatal, and killed millions of people in Europe and Asia in the 14th century.

* Smallpox: This viral disease was characterized by a rash that covered the body and could leave permanent scars. It was spread through contact with an infected person or their belongings. Smallpox was often fatal, and killed millions of people worldwide.

* Tuberculosis: This bacterial infection of the lungs was spread through the air. It caused fever, cough, and weight loss. Tuberculosis was often fatal, and killed millions of people worldwide.

* Yellow fever: This viral disease was spread by mosquitoes. It caused fever, chills, and jaundice (yellowing of the skin). Yellow fever was often fatal, and killed millions of people in Africa and South America.

* Malaria: This parasitic disease was spread by mosquitoes. It caused fever, chills, and anemia. Malaria was often fatal, and killed millions of people worldwide.