Chapter Three of Plagues and People, “Confluence of the Civilized Disease Pools of Eurasia,” describes how the growth of civilizations in Eurasia was connected to the spread of diseases. This chapter covers many events in history, but I will discuss the main ones to help illustrate McNeill’s point.

One main event in civilization history that McNeill discusses in this chapter is the establishment of the Persian empire. In the sixth century BC, the Persian empire had reached the limits of land that allowed for lucrative agriculture. McNeill emphasizes the growth and success of the Persian empire is evidence that infectious diseases were not destructive or frequent enough in this period to disrupted military and civilian life.

McNeill also discusses the rise and peaceful rule of the Han dynasty in China. He discusses how this period led to the spread Confucianism, which was a “powerful factor in the macroparasitic balance” of ancient China (McNeill 101). Essentially Confucian propaganda kept restraints on rural peasants and allowed ruling classes to keep a stable grip on power. A factor that allowed China to be peaceful and prosper in this period was the lack of frequent, debilitating diseases. Diseases were scarce in part because of the difference in climate between the north and central regions. The north was cooler and its air was less moist than central and south China. The people in the north were accustomed to their regional conditions, and the climatic differences killed insects that could carry diseases.

In contrast, McNeill explains that disease was much more frequent in India. Diseases weakened many peasants' physical abilities and made it difficult for them to produce a surplus crop. McNeill also argues that India’s caste system may have in part been a response to “epidemiological” conflict that arose with Aryan intruders. Overall, the events discussed in this chapter show how major political and social developments both influence, and are influenced by, the spread of disease.