Overview

The nineteenth century was a period of expansion of western imperialist power into Africa, Asia, the Middle East, Central and South America, and other regions of the world. This involved "population mixing" where one group of people met and lived side by side with another. Inevitably each group met a new "germ pool"—diseases specific to the other group which were now shared. Because the principles of sanitation—provision of clean water and disposal of sewage, etc.—were not fully understood yet by either the newcomers or those who were indigenous to the newly penetrated territories, neither group protected itself properly against infection and cross infection from communicable diseases.

Background

In most cases, the ways in which germs traveled from person to person and caused illnesses were not yet understood in the nineteenth century. The interest of...