Course of disease

The course of disease is shown with a simplified diagram as follows.

The course of a disease in the absence of any intervention is called the natural history of the disease. The different stages in the natural history of disease include: 

a)  Exposure to various risk factors (causative agents)

b)  Latency, period between exposure and biological onset of disease

c)  Biological onset of disease; this marks the initiation of the disease process, however, without any sign or symptom. Following biological onset of disease, it may remain asymptomatic or subclinical (i.e. without any clinical manifestations), or may lead to overt clinical disease. 

d)  Incubation (induction) period refers to variable period of time without any obvious signs or symptoms from the time of exposure.

e)  The clinical onset of the disease, when the signs and symptoms of the disease become apparent. The expression of the disease may be variable in severity or in terms of range of manifestations.

f)  The onset of permanent damage, and 

g) Death

Natural recovery, i.e. recovery without any  intervention, can occur at any stage in the progression of the disease.

References

Bezabeh ,M. ; Tesfaye,A.; Ergicho, B.; Erke, M.; Mengistu, S. and Bedane,A.; Desta, A.(2004). General Pathology. Jimma University, Gondar University Haramaya University, Dedub University.