Here’s a graph that helps understand this disease from a public health perspective.
After ingestion the virus is taken up by the gastrointestinal tract and travels by blood to the liver where it infects liver cells and replicates inside them, causing them to burst when new virus particles are released. Cell bursting releases enzymes normally inside the liver cells, such as ALT, AST, and alkaline phosphatase, and concentrations of these enzymes in the blood become abnormally high.
Some replicated viruses get into the blood and others are secreted into bile, which enters the intestine and deposits many virus particles into the intestine causing high concentrations of virus in stool. Infected people are most infectious during the period from two weeks before the appearance of symptoms until one week after symptoms began. The average incubation period (time period between infection and development of symptoms) is about 28 days, with a range of 15-50 days. This will be important to understanding the course of the epidemic in a population.
A positive test for anti-HAV IgM clinches the diagnosis of acute infection. After recovery, the IgM gradually declines, but anti-HAV IgG increases, which confers immunity against another hepatitis A infection. So, if someone has elevated blood levels of anti-HAV IgG, but not IgM, it indicates that they had a past infection that resolved.
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