Causes of Epidemics
French microbiologist Louis Pasteur established a germ theory of disease in the mid-19th century. However, it took decades for its implications to take hold, and before Pasteur’s breakthrough, various theories such as evil spirits or demons, were spread. In the early 1900s communicable diseases were still widespread, including influenza, pneumonia, smallpox, tuberculosis, diphtheria, typhoid fever and gastrointestinal diseases — all of which were often fatal. Cholera outbreaks, in particular, created terror for contracting the disease often heralded a quick death. A misunderstanding of the disease and misguided medical treatments lent legitimate fear to populations in the U.S. and worldwide.