Hepatitis Viruses - The Nasty Lineup
⭐ Hepatitis B is a DNA virus; all others (A, C, D, E) are RNA viruses.
- Classification: Grouped by genome & transmission.
- RNA Viruses: HAV, HCV, HDV, HEV
- DNA Virus: HBV
- Transmission & Chronicity:
- 📌 Vowels (A, E): Faecal-oral, Acute, No chronicity (Except HEV in immunocompromised).
- Consonants (B, C, D): Parenteral/Sexual, Chronic potential.
- Hepatitis D (Delta): Defective virus, requires HBsAg for replication; superinfection (worse) or coinfection with HBV.
Hepatitis A & E - The Fleeting Foes
- RNA viruses, faecal-oral transmission. Acute, self-limiting hepatitis; no chronic state (except rare HEV G3). 📌 Mnemonic: "Vowels to the bowels" (A & E).
| Feature | Hepatitis A (HAV) | Hepatitis E (HEV) |
|---|---|---|
| Transmission | Faecal-oral (food/water) | Faecal-oral (water); Zoonotic (pigs) |
| Incubation (wks) | 2-6 | 2-10 |
| Severity | Milder, esp. children | Severe in adults; fulminant risk |
| Diagnosis | Anti-HAV IgM | Anti-HEV IgM; HEV RNA |
| Complications | Rare: cholestatic, relapsing | Fulminant; chronic (G3, immunosuppressed) |
| Prevention | Vaccine; hygiene | Hygiene; safe water; (Vaccine not routine in India) |
| 🤰 Pregnancy | Benign | ↑↑ Mortality (20-30% 3rd trim. G1/G2) |
Hepatitis B - The Persistent Peril
⭐ The presence of HBsAg for more than 6 months defines chronic Hepatitis B infection.
- Transmission: Parenteral (needles, blood), perinatal (mother-to-child), sexual.
- Risk of Chronicity: Perinatal >90%; Early childhood 25-30%; Adult <5%.
- Key Serological Markers: 📌 Mnemonic: 'S'-Surface/Screening, 'c'-Core/Chronic, 'e'-Envelope/Extra-contagious.
| Marker | Interpretation |
|---|---|
| HBsAg | Active infection (Acute/Chronic) |
| Anti-HBs | Immunity (Vaccine/Resolved) |
| Anti-HBc IgM | Acute infection (<6 months) |
| Anti-HBc Total | Past/current exposure |
| HBeAg | High replication, ↑ infectivity |
| Anti-HBe | Low replication, ↓ infectivity (seroconv.) |
- Phases of Chronic HBV (HBsAg+ >6 months):
- Treatment Consideration (Chronic HBV): HBV DNA >20,000 IU/mL (HBeAg+) or >2,000 IU/mL (HBeAg-) with ↑ALT or significant fibrosis/cirrhosis.
Hepatitis C - The Stealthy Scourge
- RNA virus, high chronicity rate (>70%). Parenteral transmission (needles, blood).
- Genotypes: 6 major (GT 1-6). India: GT3 most prevalent, followed by GT1.
- Extrahepatic Manifestations (EHM): 📌 'C's: Cryoglobulinemia (mixed), Cutanea tarda (Porphyria), Cancer (HCC), CNS involvement, Cardiomyopathy, Membranoproliferative Glomerulonephritis (MPGN).
- Diagnosis: Anti-HCV antibodies (screen); HCV RNA PCR (confirms active infection, monitors treatment response).
- Treatment: Direct-Acting Antivirals (DAAs).
- Goal: SVR12 (Sustained Virologic Response 12 weeks post-treatment) = cure.
- Pan-genotypic regimens (e.g., Sofosbuvir/Velpatasvir) are preferred.
- ⭐ > Mixed cryoglobulinemia is a well-known extrahepatic manifestation of chronic Hepatitis C infection.
Hepatitis D - The Dependent Deviant
- Defective RNA virus; requires HBsAg for replication & transmission.
| Feature | Coinfection (HBV + HDV simultaneously) | Superinfection (HDV in chronic HBV) |
|---|---|---|
| Timing | Acute, self-limited (usually) | Acute exacerbation, often chronic |
| Severity | Severe acute hepatitis; ↑ fulminant risk | ↑↑ Fulminant hepatitis, cirrhosis risk |
| IgM anti-HDV | Transiently positive | Persistently positive |
| IgG anti-HDV | Appears late, may persist | Appears early, high titres |
- Diagnosis: Anti-HDV antibodies (IgM, IgG), HDV RNA.
- No specific treatment for HDV; HBV vaccination prevents HDV coinfection. PegIFN-alpha (low success).
High‑Yield Points - ⚡ Biggest Takeaways
- HAV: Fecal-oral transmission, acute infection only; IgM anti-HAV diagnoses.
- HBV: Parenteral/sexual transmission; chronic risk (cirrhosis, HCC); HBsAg (infection), Anti-HBs (immunity), HBeAg (infectivity).
- HCV: Primarily parenteral (IVDU); high chronic infection risk (cirrhosis, HCC); HCV RNA confirms active infection.
- HDV: Defective virus requiring HBV co-infection or superinfection (worse prognosis).
- HEV: Fecal-oral (waterborne); high mortality in pregnant women (genotypes 1,2); chronic in immunosuppressed.
- HBV window period: Anti-HBc IgM is the sole serological marker.
- Vaccines: Available for HAV & HBV; no vaccine for HCV.
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