Dengue Fever
A tropical viral illness transmitted by mosquitoes, characterized by high fever, severe body aches, and in severe cases, dangerous internal bleeding and shock.
Emergency Management: Dengue Shock Syndrome (pulse pressure < 20 mmHg or unmeasurable blood pressure). Requires aggressive IV crystalloid boluses (10-20 mL/kg over 15-30 minutes). If no response, switch to colloid solutions (e.g., Dextran 40 or Albumin).
Dengue fever is a mosquito-borne viral infection caused by one of four distinct serotypes of the Dengue virus (DENV-1 to DENV-4), a flavivirus. It is the most rapidly spreading mosquito-borne viral disease globally. The clinical spectrum ranges from a self-limiting febrile illness to severe dengue, characterized by plasma leakage, severe hemorrhage, and shock.
Detailed Overview
Dengue is transmitted primarily by Aedes aegypti mosquitoes. Infection with one serotype provides lifelong immunity to that specific serotype, but only temporary cross-immunity to the others. Paradoxically, secondary infection with a different serotype drastically increases the risk of severe dengue through a mechanism known as antibody-dependent enhancement (ADE). The critical phase of the illness occurs around the time the fever drops, where profound vascular permeability can lead to hypovolemic shock (Dengue Shock Syndrome) and multiorgan failure.
Epidemiology & Demographics
Endemic in >100 countries in tropical and subtropical regions (Southeast Asia, Americas, Western Pacific). Affects an estimated 390 million people annually, causing 500,000 hospitalizations for severe dengue and 25,000 deaths.
Etiological Mechanism
Infection by Dengue virus (DENV 1, 2, 3, or 4), an RNA virus of the Flaviviridae family. Transmitted primarily by the daytime-biting female Aedes aegypti and Aedes albopictus mosquitoes.
Primary Causes
Bite from an infected Aedes mosquito.
Following a mosquito bite, the virus replicates in local dendritic cells and regional lymph nodes, resulting in viremia. Symptoms arise from the robust immune response, particularly the release of cytokines. In primary infection, memory T and B cells are formed. If a secondary infection with a different serotype occurs, pre-existing, non-neutralizing antibodies from the first infection bind to the new virus. Instead of neutralizing it, they facilitate entry into macrophages via Fc-receptors (Antibody-Dependent Enhancement). This causes massive viral replication and a devastating 'cytokine storm' (TNF-alpha, IL-6). The cytokines severely disrupt endothelial cell tight junctions, causing profound plasma leakage into the pleural and peritoneal cavities. Simultaneously, bone marrow suppression and immune destruction cause severe thrombocytopenia, while coagulopathy leads to hemorrhagic manifestations.
Diagnostic Criteria & Guidelines
Diagnosis is suspected in patients with acute febrile illness and relevant travel history, plus two clinical signs (nausea, rash, aches, tourniquet test, leukopenia). Confirmed via viral isolation, PCR, or NS1 antigen detection in early illness, or IgM/IgG serology later.
There is no specific antiviral therapy. Management is entirely supportive. For mild cases: Acetaminophen (Paracetamol) for fever/pain. STRICT AVOIDANCE of NSAIDs (ibuprofen, aspirin) as they exacerbate bleeding risk. Oral rehydration therapy is critical.
Second-Line & Adjunctive Therapy
For Warning Signs or Severe Dengue (Critical Phase): Hospital admission and meticulous, protocol-driven IV fluid resuscitation using isotonic crystalloids (e.g., Ringer's Lactate or Normal Saline). The fluid rate must be titrated closely based on hourly urine output and hematocrit levels. Transfusion of packed RBCs if severe overt bleeding occurs. Platelet transfusions are generally NOT recommended for thrombocytopenia alone unless there is massive bleeding.
Surgical & Procedural Management
Not indicated.
Patient Counseling & Advice
Instruct the patient that the most dangerous time in Dengue is paradoxically when the fever breaks (usually around day 4-5). They must seek immediate emergency care if they develop severe abdominal pain, persistent vomiting, mucosal bleeding, or lethargy at this time. Warn explicitly against using ibuprofen or aspirin.
Follow-Up & Monitoring Schedule
Outpatient management requires daily CBC checks specifically to monitor the trend of platelets and hematocrit until the patient successfully passes the critical phase.
Preventive Strategies
Vector control is paramount. The CYD-TDV (Dengvaxia) vaccine is available, but ONLY for individuals aged 9-45 who have had a laboratory-confirmed PREVIOUS dengue infection. Giving the vaccine to seronegative individuals paradoxically increases their risk of severe dengue upon future natural infection.
For uncomplicated dengue, the prognosis is excellent with a 1-2 week recovery. However, mortality in severe dengue can approach 20% if left untreated, but drops to <1% with meticulous fluid management in a hospital setting.