## Dengue Serotypes and Severity **Key Point:** DENV-2 is historically the most virulent serotype and is most frequently associated with severe dengue manifestations (DHF/DSS) in India, particularly during epidemic years. ### Serotype Characteristics and Epidemiology | Serotype | Virulence | Geographic Pattern in India | Clinical Association | |----------|-----------|------------------------------|----------------------| | **DENV-1** | Moderate | Sporadic, increasing in recent years | Mild to moderate dengue fever | | **DENV-2** | High | Historically epidemic; major outbreaks | DHF/DSS; severe disease | | **DENV-3** | Moderate | Sporadic; emerging in some regions | Dengue fever with complications | | **DENV-4** | Low | Rare in India; limited circulation | Mild dengue fever | **High-Yield:** The 1996 dengue epidemic in India was predominantly DENV-2, which caused a large number of DHF/DSS cases. DENV-2 remains the most common cause of severe dengue in Indian epidemics. ### Mechanism of Severe Disease **Mnemonic:** **ADE** = Antibody-Dependent Enhancement Secondary infection with a different serotype (especially DENV-2 after prior DENV-1 infection) leads to cross-reactive non-neutralizing antibodies that enhance viral replication, increasing risk of DHF/DSS. **Clinical Pearl:** Sequential infection with DENV-2 as the second serotype carries the highest risk for severe dengue due to enhanced viral replication via ADE mechanism. ## Current Epidemiological Trends While DENV-1 has become increasingly prevalent in recent years (2015–2023), DENV-2 remains the serotype most strongly associated with severe disease manifestations when it does circulate.
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