Understanding Infectious Diseases: Causes, Spread, and Immune Responses
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Infectious Diseases: An Overview
Changes to body physiology that disrupt normal body functions and are caused by microorganisms are called infectious diseases. This explanation, established by Louis Pasteur and Robert Koch, is called the germ theory of disease.
Causes of Infectious Diseases
Infectious diseases are caused by various microorganisms, including:
- Viruses
- Bacteria
- Fungi
- Protists
- Parasitic worms
Disease-causing microorganisms are also called pathogens. Koch also developed a series of rules, known as Koch's postulates, that help scientists identify which organism causes a specific disease.
While many microorganisms are symbionts that are either harmless or beneficial, pathogens cause disease by:
- Destroying cells
- Disrupting body functions
- Releasing