Host invasion by microorganisms
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Introduction
One of the main causes of disease is infection by microorganisms, with four types so far identified:
- Viruses
- Bacteria
- Fungi
- Parasites- comprising protozoa and helminths
All exist as either:
- Primary pathogens (obligate): presence always corresponds with disease
- Secondary (opportunistic): prerequisites must be fulfilled before disease occurs
Microorganisms can enter the body by three routes:
- Contact: typically seen in dermatological infections
- Aerosol: typically respiratory infections
- Orofecal:typically enteric infections
Viruses
Bacteria
Parasites
References
- Murphy, K., Travers, P. and Walport, M. (2008) Janeway's Immunobiology. 7th ed. New York: Garland Science Publishing.