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Infectious Diseases

Author(s): Christine Herrmann, PhD

Infectious Diseases - Definitions

Human disease can be caused by infectious agents, genetic defects, environmental factors, or a combination of these factors. Here we will discuss only diseases brought about by infectious agents or pathogens. 

The infectious disease process begins at the time of infection, when a pathogen enters a host and starts to reproduce. Many infectious agents, though, are killed by the body’s numerous defenses before they can begin to reproduce. Furthermore, an infection may not necessarily produce disease; the infectious agent could be defeated quickly or it could hide somewhere in the body where it cannot be detected. The rapidity of onset and severity of the disease caused by an infectious agent depends on the virulence of the pathogen.