Crossroads. China was always exposed to epidemic diseases. Trade along the old silk route, war with the northern barbarians, and travel to and from India and Indochina all helped the spread of smallpox, pulmonary diseases, febrile illnesses, dysentery, and plague. With the emergence of European traders to China's southeast coast and the increase of international commercial activities in Southeast Asia during the sixteenth century, new epidemic illnesses, such as scarlet fever, cholera, diphtheria, and syphilis, appeared in the region.

Malaria. The mention of malarial fevers initially appeared in medical texts in the seventh century. Temperatures during the Tang period (618-907) were most likely higher than those of today, which meant that the diseases associated with the southern climates, such as malaria, schistosomiasis, and dengue fever, could be found further north. Some specialized treatises in the twelfth century suggested that the miasma...