Clinical Features of Dengue

Clinical presentation

Dengue begins abruptly after a typical incubation period of 5–7 days, and the course follows 3 phases: febrile, critical, and convalescent.

Early clinical findings are nonspecific. Dengue requires a high index of suspicion because recognizing early signs of shock and promptly initiating intensive supportive therapy with intravenous fluids can reduce risk of death among patients with severe dengue to <0.5%.

Laboratory findings commonly include leukopenia, thrombocytopenia, hyponatremia, elevated aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and a normal erythrocyte sedimentation rate (ESR).

Febrile Phase

• Fever typically lasts 2–7 days and can be biphasic.
• Other signs and symptoms may include severe headache, retro-orbital pain, myalgia and arthralgia, macular or maculopapular rash; and minor hemorrhagic manifestations including petechia, ecchymosis, purpura, epistaxis, gingival bleeding, hematuria, or a positive tourniquet test result.
• Some patients have injected oropharynx and facial erythema in the first 24–48 hours after onset.

Warning Signs

Warning signs of progression to severe dengue usually occur in the late febrile phase around the time of defervescence, and include persistent vomiting, severe abdominal pain, fluid accumulation, mucosal bleeding, lethargy/restlessness, postural hypotension, liver enlargement, and progressive increase in hematocrit (i.e., hemoconcentration).

Critical Phase

• The critical phase of dengue begins at defervescence and typically lasts 24–48 hours.
• Most patients clinically improve during this phase, but those with substantial plasma leakage can, within a few hours, develop severe dengue.
• Initially, physiologic compensatory mechanisms maintain adequate circulation, which narrows pulse pressure as diastolic blood pressure increases.
• Patients with severe plasma leakage may have pleural effusions, ascites, hypoproteinemia, or hemoconcentration.
• Patients may appear to be well despite early signs of shock. However, once hypotension develops, systolic blood pressure rapidly declines, and irreversible shock and death may ensue despite resuscitation.
• Patients can also develop severe hemorrhagic manifestations, including hematemesis, hematochezia, or menorrhagia, especially if they have been in prolonged shock. Uncommon manifestations include hepatitis, myocarditis, pancreatitis, and encephalitis.

Convalescent Phase

• As plasma leakage subsides, the patient enters the convalescent phase and begins to reabsorb extravasated intravenous fluids and pleural and abdominal effusions.
• As a patient's well-being improves, hemodynamic status stabilizes (although he or she may manifest bradycardia), and diuresis ensues. The patient's hematocrit stabilizes or may fall because of the dilutional effect of the reabsorbed fluid, and the white cell count usually starts to rise, followed by a recovery of platelet count.
• The convalescent-phase rash may desquamate and be pruritic.

WHO 2009 Dengue Classification

Dengue is defined by a combination of ≥2 clinical findings in a febrile person who lives in or traveled to (in the last 14 days) a dengue-endemic area. Clinical findings include nausea, vomiting, rash, aches and pains, a positive tourniquet test, leukopenia, or any warning sign.

Dengue warning signs include abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy, restlessness, and liver enlargement. Patients with warning signs should be monitored closely as they can be more likely to progress to severe disease.

Severe dengue is defined by dengue with any of the following clinical manifestations: severe plasma leakage leading to shock or fluid accumulation with respiratory distress; severe bleeding; or severe organ impairment such as hepatitis (elevated transaminases ≥1,000 IU/L), impaired consciousness, or heart impairment.