Dengue

Aka: Dengue, Break-bone Fever, Dandy Fever, Duengero Fever, Seven-day Fever, Dengue Hemorrhagic Fever, Dengue Fever, Aden Fever, Dengue Shock Syndrome

advertisement

II. Epidemiology

  1. Worldwide
    1. Incidence: 50-100 million cases/year (with 500,000 hospitalizations and 12,500 deaths)
    2. Most common Mosquito-Borne Illness worldwide (>50% of world population at risk)
  2. Endemic Regions (tropics and suptropics)
    1. Highest risk areas include Thailand, India, Indonesia, Brazil
  3. United States
    1. Incidence: Few hundred cases/year
    2. Travel to endemic area
    3. Regions in U.S. where patients may become infected with Dengue Fever
      1. Puerto Rico (endemic)
      2. Hawaii, Florida, Texas-Mexico border

III. Pathophysiology

  1. Transmitted by Aedes aegypti MosquitoSaliva (bites during daytime)
  2. Arbovirus (arthropod-borne) in the Flavivirus genus
    1. Related to West Nile Virus and Yellow Fever virus (same Flavivirus genus)
    2. Flaviviridae are enveloped, Icosahedral, single stranded RNA Viruses
    3. Flaviviridae are Message Sense RNA Viruses (Positive Stranded, +ssRNA)
      1. Message sense RNA (+ssRNA) are identical to Messenger RNA (mRNA)
      2. Like mRNA, +ssRNA may be immediately translated by host ribosomes into Protein
  3. Infects reticuloendothelial system (RBC and Platelet production organs)
    1. Liver
    2. Spleen
    3. Lymph Nodes
    4. Thymus
  4. Dengue Serotypes (one Mosquito may carry multiple serotypes)
    1. DENV 1
    2. DENV 2
      1. Second infection with Serotype 2 is associated with Dengue Hemorrhagic Fever
    3. DENV 3
    4. DENV 4
  5. Endemic areas (over 100 tropical countries with >40% of world population at risk)
    1. Southeast Asia
    2. Central America
    3. South America
    4. Caribbean
    5. Sporadic cases in southwestern U.S. along the Mexico border

IV. Symptoms

  1. Incubation
    1. Travel to endemic area within prior 14 days
    2. Abrupt flu-like symptom onset 3-15 days (typically 4-8 days) after Mosquito Bite
  2. Febrile stage (days 3-7): Dengue Fever
    1. Undulant Fever
      1. High fever falls after Day 3
      2. Fever may rise again later
    2. Severe frontal or retro-orbital Headache
    3. Nausea or Vomiting
    4. Musculoskeletal pain ("Breakbone fever")
      1. Myalgias
      2. Arthralgias
      3. Bone pain
    5. Rash
      1. Red confluent, Morbilliform rash
        1. Petechiae may also form in areas of compression (e.g. Blood Pressure cuff)
      2. Rash starts on hands and feet, then spreads to trunk
        1. See Distal Extremity Rash
  3. Severe Dengue (1% of cases)
    1. Criteria
      1. Severe if severe plasma leakage, severe Hemorrhage or severe organ Impairment
    2. Timing
      1. Follows febrile stage in a subset of patients (2-5 days after onset), typically after fever abates
    3. Risk Factors for severe Dengue
      1. Associated with prior infection and Immunity to one Dengue serotype
      2. Current, second infection with new serotype results in severe illness
    4. Herald symptoms of severe disease
      1. Abdominal Pain or tenderness
      2. Persistent Vomiting
      3. Mucosal bleeding
      4. Lethargy
      5. Hepatomegaly
      6. Heamtocrit increases with significant Thrombocytopenia
    5. Severe plasma leakage (increased vascular permeability)
      1. Third-spacing (edema, Pleural Effusion, Ascites)
    6. Dengue Hemorrhagic Fever (DHF)
      1. See Tourniquet Test as above
      2. Hemorrhage (Epistaxis, Petechiae, Purpura)
      3. Thrombocytopenia (Platelet Count <100,000)
      4. Plasma, capillary leak (hypoproteinemia, effusions)
      5. High mortality, esp. in children (mortality may approach 10%)
    7. Dengue Shock Syndrome (DSS) - lasts 48-72 hours, and has significant mortality risk
      1. Narrow Pulse Pressure (<20 mmHg)
      2. Hypotension
      3. Respiratory distress
      4. Abnormal Liver Function Tests (AST, ALT >1000)
      5. Altered Level of Consciousness
      6. Mortality rates approach 25-50% (however <1% with early and aggressive management)

V. Exam: Tourniquet test

  1. Inflate Blood Pressure cuff to midway between systolic and diastolic Blood Pressure readings
  2. Leave Blood Pressure cuff inflated for 5 minutes
  3. Release Blood Pressure cuff and wait for 2 minutes
  4. Observe for distal Petechiae
    1. At least 10-20 or more Petechiae per square inch of skin suggests capillary fragility or Thrombocytopenia

VI. Diagnosis: Consider Dengue Fever in the returning febrile traveler if the following criteria are met (WHO)

  1. Fever AND
  2. Two of the following
    1. Severe Headache
    2. Retro-orbital pain
    3. Joint Pain
    4. Myalgia
    5. Nausea
    6. Vomiting
    7. Lymphadenopathy
    8. Rash

VII. Differential Diagnosis

  1. Yellow Fever (Rare in U.S. travelers)
    1. Infects 200,000 people worldwide per year (with 30,000 deaths)
    2. Hyperbilirubinemia and Jaundice distinguish from Dengue Fever
  2. Leptospirosis
  3. Typhoid Fever
  4. Viral Hepatitis
  5. Rickettsial Disease
  6. Bacterial Sepsis
  7. Malaria
  8. Leishmaniasis

VIII. Labs

  1. Complete Blood Count
    1. Leukopenia (common)
    2. Hematocrit and Hemoglobin increased (>10% increase predicts severe disease)
    3. Thrombocytopenia with Platelets <100,000 cells/mm3 (often severe)
      1. Observe for bleeding complications
  2. Other lab findings
    1. Mild increase in liver transaminases
  3. Specific tests (confirm diagnosis, but Dengue Fever is a clinical diagnosis)
    1. Dengue IgM (after day 4) or Dengue IgG (after day 7) with 4-fold or higher increase in titers
    2. Dengue reverse transcriptase PCR (within first 5 days)
    3. Dengue non-structural Protein type 1 (NS1) detection
      1. Decreased Test Specificity in those exposed to other Flavivirus (e.g. Yellow Fever)

IX. Management

  1. No effective treatment or Vaccine
  2. General measures
    1. Maintain hydration
    2. Lower fever with Acetaminophen
    3. Avoid NSAIDS or Aspirin due to risk of Hemorrhage (as well as Reye Syndrome risk)
    4. Daily monitoring of Hematocrit and Platelet Count
  3. Hospitalization indications
    1. Infants, elderly and pregnant women
    2. Serious comorbidity (Diabetes Mellitus, unreliable social situation)
    3. Findings suggestive of impending severe Dengue
  4. Severe Dengue management
    1. Aggressive supportive care
    2. Intravenous Fluid initial protocol
      1. NS or LR 5-7 cc/kg/h for 1-2 hours
      2. then 3-5 ml/kg/h for 2-4 hours
      3. then 2-3 ml/kg/h

X. Course

  1. Incubation: 3-15 days (typically 4-8 days)
  2. Usually benign and self-limited course lasting <7 days

XI. Prevention

  1. Limit Mosquito contact (DEET, protective clothing, bed nets)
    1. See Vector borne infection
  2. New Dengue Vaccine is available in Mexico (but not in U.S.) as of 2016

XII. References

  1. Anderson (2014) Crit Dec Emerg Med 28(7): 11-9
  2. Black, Martin, DeVos (2018) Crit Dec Emerg Med 32(8): 3-12
  3. Nordurft-Froman and DeVos (2022) Crit Dec Emerg Med 36(4): 4-15
  4. Feder (2013) Am Fam Physician 88(8): 524-30 [PubMed]
  5. Huntington (2016) Am Fam Physician 94(7): 551-7 [PubMed]
  6. Mangold (2013) Pedr Emerg Care 29(5): 665-9 [PubMed]
  7. Wilder-Smith (2005) N Engl J Med 353(9): 924-32 [PubMed]

Images: Related links to external sites (from Bing)

These images are a random sampling from a Bing search on the term "Dengue." Click on the image (or right click) to open the source website in a new browser window. Search Bing for all related images

Related Topics in Viral Infection

advertisement