The pathogenesis of a disease is the biological mechanism (or mechanisms) progress of disease showing its morphological features or that leads to the diseased state. The term can also describe the origin and development of the disease, and whether it is acute, chronic, or recurrent. The word comes from the Greek πάθος pathos ("suffering", "disease") and γένεσις genesis ("creation").

Types of pathogenesis include microbial infection, inflammation, malignancy and tissue breakdown. For example, bacterial pathogenesis is the mechanism by which bacteria cause infectious illness.

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