Incubation Period for Hepatitis

Why the incubation time varies between viral types

Virus hepatitis B
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The incubation period is the amount of time between exposure to an infectious microorganism (such as a virus or bacteria) and the development of the symptoms of a disease. The incubation period varies by the type of microorganism involved and can be as short as a few days or as long as months or even years.

The incubation period should not be confused with the window period. This is the time between when a person is first infected and the moment when a blood test (or other forms of testing technology) can positively detect and confirm an infection.

The window period is important because a person is often able to infect others even if there is no confirmation that an infection has occurred.

Why the Incubation Times Differ for Hepatitis

The average incubation period for viral hepatitis varies by the viral type, the structure of the virus, and the associated route of infection.

Hepatitis A and E, for example, are primarily spread through contaminated food and drink. The virus enters the bloodstream through the lining of the throat and esophagus (called the epithelium) and makes its way to the liver where it enters and infects liver cells (hepatocytes).

Both hepatitis A and E are non-enveloped viruses, meaning that the exterior shell of the virus (capsid) does not contain the glycoproteins that enveloped viruses do. They are more virulent and will ultimately destroy the cells they infect by rupturing the cell wall (a process known as lysis).

By contrast, hepatitis B and C are primarily blood-borne viruses. Hepatitis B is most often transmitted through sex and direct blood exposure (such as through shared injecting needles). Hepatitis C is predominately spread through shared needles. The viruses will mainly infect hepatocytes but will also replicate in circulating blood cells.

Both hepatitis B and C are enveloped viruses. The process of replication tends to be slower than that of non-enveloped viruses. Instead of causing lysis, the virus will hijack the genetic machinery of the infected cell and churn out new copies of itself through a process called budding. Unlike non-enveloped viruses, the structure of an enveloped virus is such that it cannot survive inside the gastrointestinal tract.

Finally, Hepatitis D is an enveloped virus that requires the presence of hepatitis B in order to replicate.

Average Incubation Times

According to data from the Centers for Disease Control and Prevention, the average incubation period of the five most common hepatitis viruses are:

Sources:

Buchman, J. and Holmes, E. "Cell Walls and the Convergent Evolution of the Viral Envelope." Micro and Mol Bio Review. 2015; 79(4):403-18: DOI: 10.1128/MMBR.00017-15.

Centers for Disease Control and Prevention. "The ABCs of Hepatitis." Atlanta, Georgia; updated 2016.

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