The bubonic plague originated in the Gobi Desert and spread along trade routes from Asia to Europe and Africa between the 6th-17th centuries. It was carried by fleas on rats and was easily transmitted between humans. Symptoms included swollen lymph nodes, fever, vomiting and bleeding from the lungs. The plague resulted in widespread death tolls estimated at over 200 million people and significantly impacted societies and populations during the pandemic periods in the 6th century and the Black Death of 1347-1352.