Chapter 25: Hepatitis Viridae

The foundational concept involves distinguishing viral hepatitis from other liver pathologies through hepatic enzyme profiling, where viral infection triggers substantial elevation of intracellular enzymes such as alanine aminotransferase and aspartate aminotransferase due to destruction of hepatocytes, whereas obstruction of bile flow produces elevated alkaline phosphatase and gamma-glutamyl transpeptidase without comparable transaminase elevation. Hepatitis A represents a non-enveloped viral agent transmitted through fecal-oral contact that establishes acute infection followed by complete viral clearance and lifelong immunity without progression to chronic disease. Hepatitis B, a complex enveloped DNA-containing hepadnavirus, presents characteristic diagnostic antigens including the surface component detectable in blood, the core particle found within infected cells, and the envelope-associated marker useful for assessing replicative status. Interpretation of serological test results enables clinicians to identify patients experiencing primary infection, those in the diagnostic gap between antibody disappearance and appearance, individuals maintaining persistent viral infection, and those protected through vaccination or previous exposure. The chronic form of Hepatitis B infection carries substantial morbidity through progressive fibrosis advancing to end-stage liver disease and increased likelihood of developing malignant transformation. Hepatitis C demonstrates particular association with percutaneous exposure through shared injection equipment and transfusion-transmitted exposure, with the majority of infected individuals progressing toward persistent infection and associated progressive hepatic injury. Hepatitis D functions as a defective particle requiring complementation by Hepatitis B's envelope-coating glycoprotein, capable of occurring simultaneously with initial Hepatitis B infection or as superimposed infection in established carriers, both scenarios producing more severe clinical outcomes. Hepatitis E transmits through the enteric route similar to Hepatitis A but distinguishes itself through elevated fatality rates among pregnant individuals and variable progression to chronicity in immunocompromised populations.