A 45-year-old man with chronic liver disease is found to have anti-HBc (total) and HBsAg positive. Testing for anti-HBs is negative. Which is the most common cause of chronic hepatitis B infection in India?

## Hepatitis B Transmission Routes in India **Key Point:** Vertical transmission (mother-to-child) during birth is the most common cause of chronic hepatitis B infection in India and other endemic regions, accounting for the majority of chronic HBsAg carriers. ### Epidemiology of Chronic HBV in India **High-Yield:** India is an intermediate-to-high prevalence region for HBV (2–7% HBsAg prevalence depending on region). The predominant route of chronic infection acquisition is: - Vertical transmission from HBsAg-positive mothers to neonates - Risk of chronicity: ~90% in infants infected at birth, ~30% in children infected at 1–5 years - Horizontal transmission (sexual, percutaneous) typically causes acute infection with clearance in immunocompetent adults ### Serological Interpretation | Marker | Meaning | |--------|----------| | HBsAg positive | Current infection (acute or chronic) | | Anti-HBc total positive | Exposure to HBV (current or past) | | Anti-HBs negative | No immunity; not recovered | | **Interpretation** | **Chronic HBV infection** | **Clinical Pearl:** The patient's serology (HBsAg+, anti-HBc+, anti-HBs−) indicates chronic HBV. In endemic India, this pattern most commonly results from vertical transmission acquired in infancy, leading to immune tolerance and chronic carriage. ### Why Vertical Transmission Dominates in India **Mnemonic: VERTICAL** — **V**ertical transmission, **E**ndemic regions, **R**isk highest in infants, **T**ransmitted at birth, **I**mmune tolerance develops, **C**hronic carriage results, **A**dult infection usually clears, **L**ow vaccination coverage historically 1. High prevalence of HBsAg-positive women of childbearing age 2. Lack of universal neonatal HBV vaccination in earlier decades (now improving) 3. Infants infected at birth develop immune tolerance → chronic infection 4. Adult-acquired infection (sexual, percutaneous) → acute hepatitis → clearance in ~95% of immunocompetent hosts **Warning:** Do not confuse "most common route of transmission" with "most common route in a given individual." In India, while sexual and percutaneous routes occur, vertical transmission is the leading cause of the chronic HBV disease burden. [cite:Harrison 21e Ch 297; Park 26e Ch 7]