Final answer:
The disease that the Spaniards took back to the Old World was syphilis. It spread to various regions in Europe, India, China, and Japan. It was called the 'Great Pox' or the 'French Pox' among other names.
Step-by-step explanation:
The disease that the Spaniards took back to the Old World was syphilis. The disease was first described in Europe after Charles VIII of France marched his troops to Italy in 1494. When Vasco da Gama sailed around the tip of Africa in 1498, he carried the disease to India. In the 1500s, it reached China and in 1520 it reached Japan. Hernán Cortés contracted the disease in Haiti as he made his way to Mesoamerica. The disease was called the 'Great Pox' and also had names reflecting the antagonisms of the time such as the 'French Pox' or the 'Italian Pox'.