Dengue fever

Dengue virus is a positive-sense single-stranded RNA flavivirus with four antigenically distinct serotypes (DENV-1 to DENV-4), transmitted primarily by Aedes aegypti (and Aedes albopictus) mosquitoes, endemic in tropical/subtropical regions (Southeast Asia, Latin America, Caribbean, Africa). After incubation (4-14 days), classic dengue fever presents with abrupt high fever, severe frontal/retro-orbital headache, myalgias and arthralgias ('breakbone fever'), maculopapular or petechial rash (often appearing as fever resolves), and lab findings of leukopenia and thrombocytopenia. Positive tourniquet test supports diagnosis. Most cases are self-limited and resolve in 7-10 days with supportive care (fluids, acetaminophen; avoid NSAIDs/aspirin due to bleeding risk). The critical pathophysiologic concept is antibody-dependent enhancement (ADE): secondary infection with a heterologous serotype leads to non-neutralizing antibodies from the first infection binding to the new serotype, enhancing viral uptake into Fc-receptor-bearing monocytes/macrophages, triggering a massive cytokine storm. This can progress to dengue hemorrhagic fever (DHF), characterized by increased vascular permeability, plasma leakage (hemoconcentration, pleural effusions, ascites), thrombocytopenia, and hemorrhagic manifestations, and can progress to dengue shock syndrome (DSS) with hypotension and circulatory collapse—a medical emergency. Diagnosis involves NS1 antigen testing (early), IgM/IgG serology, and RT-PCR for viral RNA. There is no specific antiviral treatment; management is supportive with careful fluid management to avoid both hypovolemic shock and fluid overload. A vaccine (Dengvaxia) exists but is only recommended for those with prior confirmed dengue infection due to ADE risk in seronegative individuals. Key boards associations: flavivirus family (same as Zika, West Nile, yellow fever), Aedes aegypti vector, breakbone fever, thrombocytopenia + leukopenia, warning signs (abdominal pain, persistent vomiting, mucosal bleeding, lethargy) signaling progression to severe dengue.