Which serotype of dengue virus is most commonly associated with dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) in secondary infections?

Explanation

## Dengue Serotypes and Disease Severity **Key Point:** DENV-2 is the serotype most frequently associated with severe dengue (DHF/DSS), particularly in secondary infections. ### Serotype-Specific Pathogenicity **High-Yield:** The risk of DHF/DSS is highest in secondary dengue infection with a heterologous serotype, especially when DENV-2 is involved. This is explained by **antibody-dependent enhancement (ADE)**. ### Mechanism: Antibody-Dependent Enhancement (ADE) 1. **Primary infection** → develops immunity to one serotype (e.g., DENV-1) 2. **Secondary infection** with different serotype (e.g., DENV-2) → pre-existing antibodies bind to new virus 3. **Incomplete neutralization** → virus-antibody complexes enter macrophages via Fc receptors 4. **Enhanced viral replication** in macrophages and endothelial cells 5. **Massive cytokine release** → severe vascular permeability and shock ### Serotype Characteristics | Serotype | Epidemiology | Severity Risk | |----------|--------------|---------------| | **DENV-1** | Common in primary infections | Mild to moderate | | **DENV-2** | **Most virulent; highest DHF/DSS risk** | **Severe (especially secondary)** | | **DENV-3** | Emerging in Asia; variable severity | Moderate | | **DENV-4** | Least common; lowest virulence | Mild | **Mnemonic:** **DENV-2 = Danger** (most severe serotype in secondary infection) **Clinical Pearl:** In India, sequential infections with DENV-1 followed by DENV-2 (or vice versa) carry the highest risk of DHF/DSS in children.