In infectious disease epidemiology, a sporadic disease is an infectious disease which occurs only infrequently, haphazardly, irregularly, or occasionally, from time to time in a few isolated places, with no discernible temporal or spatial pattern, as opposed to a recognizable epidemic outbreak or endemic pattern.[1][2][3][4] The cases are so few (single or in a cluster) and separated so widely in time and place that there exists little or no discernable connection within them. They also do not show a recognizable common source of infection.[note 1]
In the discussion of non-infectious diseases, a sporadic disease is a non-communicable disease (such as cancer) which occurs in people without any family history of that disease or without any inherited genetic predisposition for the disease (change in DNA which increases the risk of having that disease).[5] Sporadic non-infectious diseases arise not due to any identifiable inherited gene, but because of randomly induced genetic mutations under the influence of environmental factors or of some unknown etiology. Sporadic non-infectious diseases typically occur late in life (late-onset), but early-onset sporadic non-infectious diseases also exist.
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