Germ theroy of disease

The germ theory of disease is a theory that identifies microorganisms as one of the main causes of disease. When proposed by Louis Pasteur this idea was highly controversial. Now however, it is considered the cornerstone of modern medicine. This idea and subsequent identification of microorganisms has allowed for innovations such as antibiotics, hygenic practices and sterilization. These things in combination have increased the life expectancy for the general public and reformed healthcare. 

This diagram is a basic flow for how an infection due to microorganisms will progress. Until the advent of the germ theory of disease, things like vaccinations would not be possible. The germ theory also allows for hospitals and surgical centers to protect both the employees and patients for harmful contamination due to germs. Below is a video provided by cine-med explaining some sterilization precautions in the OR.

sources:

http://cogsci.uwaterloo.ca/Articles/Pages/Concept.html