Lecture on Hepatitis A through E

Overview

• Discussion on hepatitis viruses A through E.
• Covers epidemiology, etiology, virology, pathophysiology.
• Focus on serology relevant to board exams.

Key Aspects of Hepatitis Viruses

Hepatitis A Virus (HAV)

• Infection Type: Acute.
• Transmission: Fecal-oral route; mnemonic: A for anus.
• Structure: No envelope, positive-sense single-stranded RNA.

Hepatitis B Virus (HBV)

• Infection Type: Both acute and chronic.
• Transmission: Sexual intercourse, blood, perinatal.
• Structure: Enveloped, partially double-stranded DNA, retrovirus with reverse transcriptase.

Hepatitis C Virus (HCV)

• Infection Type: Both acute and chronic.
• Transmission: Similar to HBV (sex, blood, perinatal).
• Structure: Enveloped, positive-sense single-stranded RNA.

Hepatitis D Virus (HDV)

• Infection Type: Mainly chronic.
• Transmission: Similar to HBV and HCV.
• Dependency on HBV: Requires HBV for infection (co-infection or superinfection).
• Structure: Enveloped, negative-sense circular single-stranded RNA.

Hepatitis E Virus (HEV)

• Infection Type: Mainly acute.
• Transmission: Fecal-oral route; mnemonic: E for eat.
• Structure: No envelope, positive-sense single-stranded RNA.

Viral Infection Mechanism

• RNA Viruses (HAV, HEV, HCV, HDV)
  • Enter host cell via endocytosis, use ribosomes to synthesize proteins.
  • Replication through RNA-dependent RNA polymerase.
• DNA Virus (HBV)
  • Enters cell, converts partial double-stranded DNA to complete with host enzymes.
  • Uses reverse transcriptase for replication.

Pathophysiology

• Cell Infection and Damage
  • Viruses cause hepatocyte death through direct lysis and immune response.
  • Immune system attacks infected cells via CD8 T-cells, causing apoptosis.
• Cytokine Production
  • Inflammation leads to cytokine release, affects CNS causing fever and malaise.

Clinical Manifestations

Prodromal Phase

• Symptoms: Fever, nausea, vomiting, malaise, diarrhea.

Icteric Phase

• Symptoms: Jaundice (scleral and skin), dark urine, clay-colored stools, hepatomegaly.
• Lab Findings: Elevated bilirubin, liver enzymes (AST, ALT), prolonged PT/INR and PTT.

Convalescent Phase

• Symptoms and lab abnormalities begin to resolve.

Extrahepatic Manifestations (Primarily HBV, HCV)

• Immune complexes affect other tissues, causing arthritis, vasculitis, myocarditis, glomerulonephritis.
• May cause hematological effects: Thrombocytopenia, hemolytic anemia, neutropenia.

Chronic Infection Risks (HBV, HCV, HDV)

• Chronic infection can lead to fibrosis, cirrhosis, and increased risk of hepatocellular carcinoma.

Summary

• Discussion on hepatitis viruses A through E: transmission, types of infection, structure, and clinical implications.
• Detailed pathophysiology and progression of liver damage.
• Emphasis on serological markers and clinical manifestations for exam preparation.