Acute Viral Hepatitis (AVH) is a systemic infection that predominantly affects the liver, caused by hepatotropic viruses including hepatitis A, B, C, D, and E . These viruses trigger liver inflammation and hepatocellular injury. The clinical course may be self-limiting or progress to chronic liver disease, cirrhosis, hepatic failure, or hepatocellular carcinoma.
Etiological Agents
| Virus | Genome Type | Transmission | Chronicity | Vaccine Available |
|---|---|---|---|---|
| HAV | RNA | Fecal-oral | No | Yes |
| HBV | DNA | Parenteral, sexual, perinatal | Yes | Yes |
| HCV | RNA | Parenteral | Yes | No |
| HDV | RNA (requires HBV) | Parenteral | Yes | No (preventable with HBV vaccine) |
| HEV | RNA | Fecal-oral | Rare (mainly in immunocompromised) | Limited use |
🔑 High-Yield: Only HBV is a DNA virus; the others are RNA viruses.
Other Viral Causes of Hepatitis
- Cytomegalovirus (CMV)
- Herpes Simplex Virus (HSV)
- Epstein-Barr Virus (EBV)
- Adenovirus
- Coxsackievirus
These are more common in immunocompromised hosts.
Pathophysiology
All hepatitis viruses are non-cytopathic; liver injury is primarily immune-mediated. CD8+ T cells recognize infected hepatocytes and trigger inflammation and hepatocyte apoptosis.
Transmission Routes
- HAV & HEV : Fecal-oral route (contaminated food/water)
- HBV, HCV & HDV : Parenteral, sexual contact, perinatal
- Common Risks :
- Unsafe injections or medical procedures
- Blood transfusion (especially pre-1992 for HCV)
- IV drug use
- High-risk sexual behaviors
- Travel to endemic regions
⚠️ High-Yield: HDV requires co-infection or superinfection with HBV for replication.
Individual Virus Overviews
Hepatitis A Virus (HAV)
- Family : Picornaviridae
- Genome : ssRNA, non-enveloped
- Incubation : ~28 days
- Course : Self-limited; no chronic infection
- Serology :
- Anti-HAV IgM → acute infection
- Anti-HAV IgG → past infection/immunity
Risk Factors : Poor sanitation, travel to endemic areas, MSM, IV drug users.
💉 Vaccine : Available and effective
Hepatitis B Virus (HBV)
- Family : Hepadnaviridae
- Genome : dsDNA, enveloped
- Incubation : 60–150 days
- Course : Can become chronic (especially in neonates)
Key Serologic Markers :
| Marker | Interpretation |
|---|---|
| HBsAg | Active infection |
| anti-HBs | Immunity (vaccine or recovery) |
| HBeAg | High infectivity |
| anti-HBe | Lower infectivity |
| anti-HBc IgM | Recent infection |
| anti-HBc IgG | Past/chronic infection |
Chronic Complications : Cirrhosis, hepatocellular carcinoma (HCC)
💉 Vaccine : Highly effective; given at birth and during infancy
Hepatitis C Virus (HCV)
- Family : Flaviviridae
- Genome : ssRNA, enveloped
- Incubation : 2–12 weeks
- Course : High rate of chronicity (60–85%)
- Transmission : Blood exposure, IV drug use
No vaccine available. Direct-acting antivirals (DAAs) achieve >95% cure.
Hepatitis D Virus (HDV)
- Genus : Deltavirus
- Genome : Circular ssRNA
- Dependent on : HBV for replication
- Forms :
- Coinfection (with HBV): Usually self-limited
- Superinfection (in chronic HBV): High risk of fulminant hepatitis and chronicity
Hepatitis E Virus (HEV)
- Family : Hepeviridae
- Genome : ssRNA
- Transmission : Fecal-oral (contaminated water)
- Severity : More severe in pregnant women (especially 3rd trimester)
💉 Vaccine : Available in some countries (e.g., China)
Clinical Phases of AVH
- Prodromal Phase (1–2 weeks)
- Flu-like symptoms: Fever, malaise, anorexia, nausea, vomiting
- Arthralgia, myalgia, pharyngitis, headache
- Dark urine, pale stools
- Icteric Phase
- Jaundice (scleral/skin), hepatomegaly, RUQ tenderness
- Constitutional symptoms often improve
- Cholestatic picture in some cases
- Convalescent Phase
- Gradual resolution
- Residual hepatomegaly, biochemical abnormalities
Complications
- Fulminant hepatic failure (more with HDV, HBV)
- Chronic hepatitis (especially with HBV, HCV, HDV)
- Cirrhosis
- Hepatocellular carcinoma
Diagnosis
- Liver Function Tests (LFTs) :
- ↑ ALT, AST (ALT > AST typically)
- ↑ Bilirubin
- ↑ ALP (if cholestatic pattern)
- Serologic Tests : Based on specific virus
- Molecular Tests : PCR for viral RNA/DNA quantification
🎯 High-Yield: Jaundice becomes clinically evident when serum bilirubin >2.5 mg/dL (>43 μmol/L)
Management
- Supportive care for acute hepatitis (hydration, rest, avoid hepatotoxins)
- Hospitalization for fulminant hepatitis or complications
- Antivirals :
- Chronic HBV: Entecavir, Tenofovir
- Chronic HCV: DAAs (e.g., Sofosbuvir + Ledipasvir)
❌ Avoid acetaminophen and alcohol
Prevention
- Vaccination : HAV, HBV
- Safe practices : Clean water, food hygiene, safe sex, sterile medical equipment
- Screening : Pregnant women for HBV, blood donors for HBV/HCV
Prognosis
- HAV & HEV : Excellent in most; full recovery expected
- HBV & HCV : Risk of chronic disease; prognosis depends on early detection and treatment
- HDV : Worse prognosis when superimposed on chronic HBV
High-Yield Summary Table
| Feature | HAV | HBV | HCV | HDV | HEV |
|---|---|---|---|---|---|
| Genome | RNA | DNA | RNA | RNA | RNA |
| Chronic? | No | Yes | Yes | Yes | Rare |
| Vaccine | Yes | Yes | No | No (HBV prevention) | Limited |
| Transmission | Fecal-oral | Blood, sex, perinatal | Blood | Blood (needs HBV) | Fecal-oral |
| Risk in Pregnancy | Low | Moderate | Moderate | High if co-infected | Very high (3rd trimester) |
