dengue
DENGUE

Dengue infection is caused by the dengue virus that belongs to the family Flaviviridae. It is generally self-limiting and rarely fatal.
There are 4 serotypes (DEN-1, DEN-2, DEN-3, DEN-4). Infection w/ dengue serotype confers lifetime protective immunity to that specific serotype; cross-protection for other serotypes is only short-term.
It is transmitted to humans through the bites of infected Aedes mosquitoes. It is primarily transmitted by female Aedes aegypti, a tropical and subtropical species.Humans & monkeys are the amplifying hosts after the mosquito bite.
After 4-10 days of incubation period, illness begins immediately.
The acute phase of illness lasts for 3-7 days, but the convalescent phase may be prolonged for a week and may be associated with weakness and depression especially in adults.

Introduction

Dengue Fever (DF)

  • Dengue fever is generally a self-limiting & is rarely fatal
  • The acute phase of illness lasts for 3-7 days, but the convalescent phase may be prolonged for a week & may be associated with weakness & depression especially in adults

Dengue Hemorrhagic Fever (DHF)

  • During the acute phase of illness, it is difficult to distinguish DHF from DF & other febrile illnesses; thus, accurate diagnosis can only be made once fever remits
    • Major differentiating changes include abnormal hemostasis & plasma leakage into the abdominal & pleural cavities

Etiology

  • Etiologic agent: Dengue virus, from the family Flaviviridae
    • 4 serotypes: DEN-1, DEN-2, DEN-3 & DEN-4
    • Infection with a dengue serotype confers lifelong immunity to that specific serotype; cross-protection for other serotypes is only short term
  • Vector: Aedes (Stegomyia) mosquitoes
  • Transmission: Humans & monkeys are the amplifying hosts after a mosquito bite
  • Incubation period
    • Extrinsic (within mosquito vector): 8-10 days
    • Intrinsic (within human host): 3-14 days (average of 4-7 days)

Signs and Symptoms

Dengue Fever (DF)

  • Older children & adults:
    • Mild febrile syndrome or high fever with abrupt onset, may be biphasic (high fever that becomes normal then recurs to its previous degree) & usually lasts for 2-7 days
    • Severe headache, pain behind the eyes, general malaise, muscle or joint pains, nausea & vomiting, rash
    • Hemorrhagic manifestations eg epistaxis, gingival bleeding, hematuria, menorrhagia, skin hemorrhages (petechiae, purpura, ecchymoses), gastrointestinal (GI) bleeding (hematemesis, melena, hematochezia)
  • Infants & young children: Undifferentiated fever & maculopapular rash are common

Atypical Presentation

  • Acute abdominal pain, diarrhea, severe GI hemorrhage
  • Severe headache, convulsions, altered sensorium
  • Encephalitic signs associated with or without intracranial hemorrhage
  • Irregular pulse & heart rate
  • Respiratory distress
  • Fulminant hepatic failure, obstructive jaundice, raised liver enzymes, Reye syndrome
  • Acute renal failure
  • Disseminated intravascular coagulation (DIC)
  • Vertical transmission in newborns

Dengue Hemorrhagic Fever (DHF)

  • The critical stage in DHF is at the time of defervescence, ie the phase of plasma leakage, but signs of circulatory failure or hemorrhagic manifestations may occur from about 24 hours before to 24 hours after the temperature falls to normal
  • 4 Major Clinical Manifestations:
    • High fever
    • Hemorrhagic phenomena: Scattered petechiae are the most common hemorrhagic manifestations
    • Hepatomegaly
    • Circulatory failure
  • In children, the following may be observed:
    • Sudden rise in body temperature accompanied by facial flush
    • Nonspecific constitutional symptoms resembling dengue fever (DF) eg anorexia, vomiting, headache & muscle or bone & joint pain
    • Epigastric discomfort, tenderness at the right costal margin & generalized abdominal pain
    • Fever of 40-41°C & febrile convulsions in infants

Dengue Shock Syndrome (DSS)

  • Circulatory failure
    • Skin becomes cool, blotchy & congested
    • Circumoral cyanosis
    • Rapid, weak pulse with narrowing of the pulse pressure
    • Hypotension with cold clammy skin
  • May initially be lethargic then becomes restless & rapidly enters a critical stage of shock
  • Acute abdominal pain
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