phases of dengue infection
Three distinct phases can be identified in dengue infection:
- febrile phase
- usually lasts 2-7 days
- patients present with
- sudden onset of high grade fever accompanied by facial flushing, skin erythema, generalized body aches, myalgia, arthralgia, retro-orbital eye pain, photophobia, and headache
- anorexia, nausea and vomiting are common
- sore throat, an injected pharynx and conjunctival injection may be seen in some patients
- patients may suffer an acute and progressive difficulty in carrying out normal functions e.g. – work, schooling etc.
- difficult to differentiate dengue from non-dengue febrile illness during this phase
- haemorrhagic manifestations may be present – petechiae, mucosal bleeding etc
- liver may be enlarged and tender
- full blood count may indicate a progressive decrease in white cell count which is one of the earliest signs and should alert the physician to a high probability of dengue
- patients should be monitored for warning signs and other clinical parameters for the development of the critical phase
- critical phase
- during the transition from febrile to afebrile phase. patient enters a period of highest risk for developing the severe manifestations of plasma leak and hemorrhage
- usually starts around the time of defervescence (between day 3-8 of the illness)
- the following warning signs usually precede the manifestations of shock (may occur at or after defervescence)
- abdominal pain or tenderness
- persistent vomiting
- accumulation of clinical fluid (e.g. - ascites, pleural effusion)
- spontaneous mucosal bleeding
- lethargy or restlessness
- liver enlargement >2 cm
- increase in haematocrit with rapid decrease in platelet count
- the period of clinically significant plasma leakage usually lasts between 24-48 hours.
- patients with plasma leak should be monitored for early signs of circulatory collapse e.g. - cool extremities, narrowing pulse pressure, delayed capillary refill etc
- once a patient experiences frank shock he or she will be categorized as having DSS
- convalescent phase
- patients who survives the 24-48 hour critical period will begin to reabsorb the fluids that leaked from the intravascular space (i.e., plasma and administered intravenous fluids)
- the following may be observed during this period
- patient will report a sense of improved well being, return of appetite
- stabilizing vital signs (widen pulse pressure, strong palpable pulse)
- bradycardia
- hematocrit levels returning to normal or low due to dilutional effects of the reabsorbed fluid
- increased urine output
- appearance of the characteristic rash - a confluent sometimes pruritic, erythematous or petechial rash with multiple small round islands of unaffected skin described as “isles of white in the sea of red”
- WBC may increase soon after defervescence but platelet count takes a longer time than WBC’s to become normal (1,2,3)
In dengue haemorrhagic fever or dengue shock syndrome all three stages can be observed. In dengue fever, critical phase is normally bypassed (1).
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