## Dengue Serotypes and Hemorrhagic Fever **Key Point:** DENV-2 is classically associated with severe dengue hemorrhagic fever, particularly in secondary infections due to antibody-dependent enhancement (ADE). **High-Yield:** Dengue Hemorrhagic Fever (DHF) Pathophysiology: - Occurs predominantly in secondary dengue infection (heterologous serotype) - Antibody-dependent enhancement (ADE): non-neutralizing antibodies from primary infection enhance viral replication in secondary infection - DENV-2 has been the most virulent serotype historically, causing the largest DHF epidemics in India and Southeast Asia - Increased vascular permeability leads to plasma leakage, thrombocytopenia, and hemorrhagic manifestations ## Serotype Distribution in India | Serotype | Epidemiological Role | Geographic Distribution | |----------|----------------------|-------------------------| | DENV-1 | Causes epidemics; mild to moderate | Pan-India | | DENV-2 | Most severe; DHF/DSS | South India, endemic areas | | DENV-3 | Emerging; moderate severity | Parts of India | | DENV-4 | Least common; rare | Sporadic | **Mnemonic:** **DENV-2 = Danger** (most severe serotype in secondary infection) **Clinical Pearl:** The 2015-2017 dengue epidemics in India were predominantly DENV-2, correlating with increased DHF cases. Co-circulation of multiple serotypes increases DHF risk. [cite:Park 26e Ch 9]
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