The virus is ingested with contaminated food or water or from oral contact with contaminated hands. It infects the intestinal tract and is then transported to the liver (Fig. 1). The exact area of infection in the gastrointestinal tract is not known. Infectious particles appear in the blood for only about a week at most, although, as mentioned above, investigations by nested RT-PCR have shown that the duration of viremia may be considerably longer than initially thought. The liver is essentially the only target organ of the virus. This means that the hepatocyte is the only cell in which the virus replicates. HAV is then transported back to the gastrointestinal tract via the biliary tree.
The typical HAV pathology of the liver includes necro-inflammatory lesions in the hepatic parenchyma. The pathogenesis of hepatitis A infection does not involve direct viral cytopathology but is rather due to the host immune response. It is also not due to antibody responses to the virus.
The pathogenesis is essentially a cell-mediated immune injury—specifically the CD8 T-lymphocyte response and various inflammatory cytokines. Apoptosis or programmed cell death also plays a major role.
Excretion in feces
FIGURE 1 Pathogenesis of Hepatitis A virus.
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