Table 1.7 Incubation Periods of Selected Exposures and DiseasesĪlthough disease is not apparent during the incubation period, some pathologic changes may be detectable with laboratory, radiographic, or other screening methods. The latency period for leukemia to become evident among survivors of the atomic bomb blast in Hiroshima ranged from 2 to 12 years, peaking at 6–7 years.( 44) Incubation periods of selected exposures and diseases varying from minutes to decades are displayed in Table 1.7. For example, the typical incubation period for hepatitis A is as long as 7 weeks. Even for a single disease, the characteristic incubation period has a range. This period may be as brief as seconds for hypersensitivity and toxic reactions to as long as decades for certain chronic diseases. During this stage, disease is said to be asymptomatic (no symptoms) or inapparent. This stage of subclinical disease, extending from the time of exposure to onset of disease symptoms, is usually called the incubation period for infectious diseases, and the latency period for chronic diseases. For cancer, the exposure may be a factor that initiates the process, such as asbestos fibers or components in tobacco smoke (for lung cancer), or one that promotes the process, such as estrogen (for endometrial cancer).Īfter the disease process has been triggered, pathological changes then occur without the individual being aware of them. For an infectious disease, the exposure is a microorganism. The process begins with the appropriate exposure to or accumulation of factors sufficient for the disease process to begin in a susceptible host.
Department of Health and Human Services 1992. Source: Centers for Disease Control and Prevention. Figure 1.18 Natural History of Disease Timeline
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