Dengue Fever

Introduction

Dengue is a febrile illness caused by infection with 1 of 4 dengue viruses (DENV) transmitted by Aedes aegypti or Aedes albopictus mosquito.

  • In Malaysia, all 4 serotypes can be isolated at any given time.
  • Each episode of infection induces a life-long protective immunity to the homologous serotype but confers only partial and transient protection against other serotypes.
  • Secondary infection with a different serotype is a major risk factor for severe dengue due to antibody-dependent enhancement.



Symptoms

The incubation period of DENV infection ranges from 3 to 14 days; symptoms typically develop between 4 and 7 days after the bite of an infected mosquito.

Clinical Course of Dengue Fever

Dengue Case Classification by Severity

Phases of infection

  • Febrile phase
    • Patients typically develop a sudden high-grade fever. This acute febrile phase usually lasts 2-7 days and is often accompanied by headache, vomiting, myalgia, arthralgia, eye pain and a transient macular rash in some cases.
  • Critical phase
    • Only seen in severe dengue or dengue with warning signs.
    • Around the time of defervescence (typically days 3 to 7 of infection), a small proportion of patients develop a systemic vascular leak syndrome characterized by plasma leakage, bleeding, shock and organ impairment. This critical phase lasts for 24 to 48 hours.
    • Moderate-to-severe thrombocytopenia is common during the critical phase; nadir platelet counts ≤20,000 cells/mm3 may be observed, followed by rapid improvement during the recovery phase. A transient increase in the activated partial-thromboplastin time and decrease in fibrinogen levels are also common.
  • Recovery phase
    • During the recovery phase, plasma leakage and haemorrhage resolve, vital signs stabilize, and accumulated fluids are resorbed.
    • An additional rash (a confluent, erythematous eruption with small islands of unaffected skin that is often pruritic; "islands-of-white-in-a-sea-of-red") may appear during the recovery phase (within 1-2 days of defervescence and lasting 1-5 days).
    • The recovery phase typically lasts 2-4 days; adults may have profound fatigue for days to weeks after recovery.




Treatment

Outpatient management is appropriate for patients with presumptive diagnosis of dengue in the absence of warning signs or coexisting condition (pregnancy, infancy, old age, diabetes, renal failure, underlying haemolytic disease, obesity or poor social situation).

  • Take plenty of fluids and watch for signs of dehydration.
  • Fever and myalgias should be managed with paracetamol
    • May perform tepid sponging if the patient still has a high fever.
    • Aspirin or NSAIDs should be avoided as these aggravate gastritis or bleeding.
  • Patients should be instructed regarding the warning signs of severe dengue infection.

Early recognition of progression to severe disease and patients at increased risk for severe disease is essential, with prompt initiation of more aggressive therapy when necessary.

  • Regular monitoring of vital signs, haematocrit and urine output (goal: 0.5 to 1 ml/kg/hour).
  • In mild cases, particularly when medical attention is received early, oral rehydration may be sufficient.
  • Administration of intravenous fluid is warranted in patients with established intravascular volume loss.
  • Blood transfusion is appropriate in patients with significant bleeding or low haematocrit and failure to improve with fluid resuscitation.



Prevention

Mosquito control

Personal protective measures

  • Wear clothing that reduces the amount of exposed skin.
  • Using an effective mosquito repellents, such as DEET.

Vaccine development

  • CYD-TDV (Dengvaxia) vaccine should be administered only to individuals with history of previous DENV infection or laboratory evidence of previous DENV infection.



Food and Supplements

Food and supplements such as Carica papaya leave juice/extract, cactus extract, crab or padi frog soup, bitter gourd soup, porcupine bezoar stone, Tawa-tawa and Pegaga leaves and commercial isotonic drink have not been proven scientifically with robust evidence in preventing complications, expediting the recovery or curing dengue infection.



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