In a screening program for blood donors in a tertiary hospital in Mumbai, the most common cause of chronic viral hepatitis identified is which of the following?

Explanation

## Chronic Viral Hepatitis: Global and Indian Epidemiology **Key Point:** Hepatitis B virus (HBV) is the most common cause of chronic viral hepatitis globally and in India, affecting approximately 40 million people in India alone. ### Chronicity Potential of Hepatitis Viruses | Virus | Acute Infection | Chronic Infection | Chronicity Rate | Clinical Significance | |-------|-----------------|-------------------|-----------------|----------------------| | HAV | Yes | No | 0% | Self-limited; no carrier state | | HBV | Yes | Yes | 5–10% (adults); 90% (neonates) | Major cause of cirrhosis, HCC | | HCV | Yes | Yes | 70–80% | Silent progression; high HCC risk | | HDV | Yes (co-infection) | Yes (with HBV) | 70–80% | Severe disease; requires HBsAg+ | | HEV | Yes | Rare (immunocompromised) | <1% | Fulminant in pregnancy | **High-Yield:** In India, HBV prevalence is 2–3% in the general population and 5–10% among blood donors. HCV prevalence is lower (0.5–1%), making HBV the dominant cause of chronic hepatitis in blood donor screening. ### Why HBV Causes Chronic Infection 1. **Incomplete viral clearance:** In ~5–10% of immunocompetent adults, the immune response fails to eliminate HBsAg 2. **Integration into host genome:** HBV DNA integrates into hepatocyte DNA, allowing persistent replication 3. **Immune tolerance:** Particularly in perinatally infected individuals (90% chronicity in neonates) 4. **Viral escape mutations:** HBV can evade immune recognition through surface antigen mutations **Clinical Pearl:** Chronic HBV is defined as HBsAg positivity for >6 months. Screening blood donors for HBsAg is mandatory in India (NACO guidelines) to prevent transfusion-transmitted infection. ### Distinction from Other Hepatitis Viruses **Key Point:** HAV never causes chronic infection — it is always self-limited. HEV rarely causes chronicity except in severely immunocompromised patients (e.g., solid organ transplant recipients). HCV causes chronic infection in 70–80% of cases but is less prevalent in Indian blood donors than HBV.