Dengue

Dengue virus has four serotypes (DENV 1–4), transmitted by the day-biting Aedes aegypti mosquito (peak activity 6 AM–6 PM, urban areas, breeds in small collections of standing water). First infection with any serotype is usually mild or asymptomatic. Second infection with a DIFFERENT serotype carries significantly higher risk for severe dengue due to antibody-dependent enhancement. Presentation: sudden high fever (40°C, 'breakbone fever'), severe retro-orbital headache, myalgia, arthralgia, and a maculopapular rash appearing 3–5 days after fever onset. Laboratory findings include leukopenia and thrombocytopenia. Dengue hemorrhagic fever (DHF) warning signs typically appear around defervescence (day 3–7 as fever breaks): persistent vomiting, severe abdominal pain, mucosal bleeding (gingival, epistaxis, vaginal), restlessness or lethargy, hepatomegaly >2 cm, and the critical laboratory finding — rising hematocrit concurrent with rapidly falling platelet count. This combination indicates plasma leakage from increased vascular permeability. Dengue shock syndrome (DSS): progression to circulatory failure with narrow pulse pressure (<20 mmHg), weak rapid pulse, cold clammy extremities, altered consciousness. Diagnosis: NS1 antigen testing (positive in first 5 days), IgM/IgG serology (positive after day 5). The tourniquet test (inflate BP cuff between systolic and diastolic for 5 minutes; ≥20 petechiae per 1-inch square is positive) serves as a bedside screening tool. Treatment: NO antiviral exists. Management is entirely supportive. Oral rehydration is first-line for mild cases. IV isotonic crystalloids (normal saline or lactated Ringer's) for DHF with signs of plasma leakage — the goal is to maintain adequate circulation during the 24–48 hour critical phase. Acetaminophen for fever and pain — aspirin and NSAIDs are CONTRAINDICATED (increase bleeding risk in thrombocytopenic patients). Platelet transfusion only for active hemorrhage, not for a low count alone. Serial monitoring: hematocrit and platelet count every 4–6 hours during the critical phase. Prevention: eliminate standing water (breeding sites), use insect repellent, window screens, long sleeves during daytime. Dengvaxia vaccine has limited indications. Nursing: implement bleeding precautions (soft toothbrush, electric razor, no IM injections, avoid rectal temperatures), strict I&O with daily weights, monitor for signs of shock (restlessness, tachycardia, narrowing pulse pressure), and educate that the most dangerous phase is when the fever BREAKS, not when it's highest.