dengue virus

Dengue virus is a single-stranded, positive-sense RNA virus of the Flaviviridae family, with four distinct serotypes (DENV-1 to DENV-4). It is transmitted by Aedes mosquitoes, primarily in tropical and subtropical regions. After an incubation period of 4-14 days, patients typically develop an acute febrile illness with severe headache, retro-orbital pain, myalgias, arthralgias ('breakbone fever'), and a maculopapular rash that may show a characteristic 'islands of white in a sea of red' pattern. Laboratory findings often include leukopenia, thrombocytopenia, and elevated hematocrit. Most cases are self-limited and resolve within a week. However, secondary infection with a heterologous serotype can lead to severe dengue (dengue hemorrhagic fever/dengue shock syndrome) via antibody-dependent enhancement (ADE), where non-neutralizing antibodies from the primary infection enhance viral entry into Fc-receptor-bearing cells, triggering a cytokine storm, increased vascular permeability, plasma leakage, hemorrhage, and shock. Warning signs for severe disease include abdominal pain, persistent vomiting, mucosal bleeding, lethargy, and rapid drop in platelet count with rising hematocrit. Diagnosis involves NS1 antigen testing (early), IgM/IgG serology, or RT-PCR. Management is supportive (fluid resuscitation, careful monitoring), as no specific antiviral therapy exists; NSAIDs/aspirin should be avoided due to bleeding risk. A vaccine (Dengvaxia) is available but recommended only for those with prior confirmed dengue infection due to ADE concerns in seronegative individuals.