Aetiology,pathophysiology and diagnosis of dengue infection
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Aetiology,pathophysiology and diagnosis of dengue infection

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Aetiology,pathophysiology and diagnosis of dengue infection Aetiology,pathophysiology and diagnosis of dengue infection Presentation Transcript

  • AETIOLOGY,PATHOPHYSIOLOGY AND DIAGNOSIS OF DENGUE INFECTION DR LEE OI WAH PEG. PERUBATAN UD54
  • Dengue Virus
    • Causes dengue and dengue hemorrhagic fever
    • Is an arbovirus
    • Transmitted by mosquitoes
    • Composed of single-stranded RNA
    • Has 4 serotypes (DEN-1, 2, 3, 4)
  • Dengue Viruses
    • Each serotype provides specific lifetime immunity, and short-term cross-immunity
    • All serotypes can cause severe and fatal disease
    • Genetic variation within serotypes
    • Some genetic variants within each serotype appear to be more virulent or have greater epidemic potential
  • Serotype Surveilan Di Ng Perak 2002 - 2007 Year No of Samples Type 1 Type 2 Type 3 Type 4 2002 113 0 1 1 2 2003 22 0 0 0 0 2004 8 0 1 0 0 2005 250 4 1 3 2 2006 160 4 0 4 1 2007 243 9 19 7 0 Total 796 17 22 15 5
  • DENGUE VECTORS Aedes aegypti Aedes albopictus
  • Larva Pupa 1 - 2 Days 1 - 3 Days 6 - 8 Days 2 - 3 Days Water LIFE CYCLE OF THE AEDES Adult Eggs Hatch 1- 48 hrs Complete cycle 9 – 10 days
  • DENGUE TRANSMISSION Infected Person Susceptible Person Mosquito Bite Infected Mosquito Infected Mosquito Bites next person Becomes Sick Mosquito Bite Infected Mosquito 3 – 14 days later Remains viremic 2 to 10 Days 8 – 12 DAYS
  • Manifestations of the dengue syndrome Asymptomatic Undifferentiated fever No h'rage Unusual hemorrhage Dengue Fever DHF I & II DSS Dengue Hemorrhagic Fever ( plasma leakage) Symptomatic Dengue virus Infection
    • Fever lasting 2-7 days, occasionally biphasic
    • Bleeding tendencies
    • Thrombocytopenia (100,000/mm3 or less)
    • Evidence of plasma leakage: Haemoconcentration (20% above baseline)
    • A drop in haematocrit following fluid replacement
      • Pleural effusion, ascites (not obvious in early stage of critical phase), circulatory disturbances.
    • Hypovolemic shock
    Dengue Haemorrhagic Fever (WHO 1997)
  • Dengue Shock Syndrome (WHO 1997) All the above 4 criteria for DHF, plus evidence of circulatory failure: rapid and weak pulse narrow pulse pressure less than 20mmHg or hypotension for age cold clammy skin and restlessness
  • WHO grading of DHF/DSS (WHO 1997 ) Grade 1 In the presence of haemoconcentration, fever and symptoms, a positive TT Grade 2 spontaneous bleeding in addition to the manifestation from Grade 2 Grade 3* circulatory failure, pulse pressure less than 20 mmHg but systolic pressure normal Grade 4* profound shock, hypotension or unrecordable blood pressure. Simplification: Grade 1 & 2: Non-shock DHF Grade 3: COMPENSATED shock Grade 4: DECOMPENSATED shock #
  • Dengue Case Classification Dengue Perak 5/2010
    • PATHOPHYSIOLOGY OF DENGUE INFECTION
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  • Deferversence 24-48 hours
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    • Recognition of onset of reabsorption phase is also important because i.v fluid regime needs to be progressively reduced/ discontinued at this stage.
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  • Thrombocytopenia
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  • 120 110 100 90 80 70 60 Blood pressure, pulse pressure, heart rate in hypovolemic shock Time LCS Lum Compensated shock Decompensated shock First sign of shock is tachycardia Followed by increasing diastolic BP Drop is systolic BP is relatively late event PR
    • DIAGNOSIS OF DF OR DHF
  • Important points to evaluate:
    • History:
    • date of onset of fever/ illness
    • nausea, vomiting, abdominal pain, diarrhoea
    • bleeding tendency
    • change in mental state/seizure/dizziness
    • urine output (frequency, volume and time of last voiding)
    • other important relevant histories:
      • family or neighbourhood history of dengue
      • jungle trekking and swimming in waterfall (consider leptospirosis, typhus, malaria)
      • travelling
      • recent unprotected sexual or drug use behaviour (consider acute HIV seroconversion illness)
      • co-morbidities (consider sepsis in patients with diabetes mellitus)
  • Physical examination:
      • Assess mental state and GCS score
      • Assess haemodynamic status
          • Cold/ warm extremities
          • Capillary filling time (normal < 2 seconds);
          • Pulse rate and Pulse volume
          • Blood pressure and Pulse pressure
      • Look out for tachypnoea/ acidotic breathing/ pleural effusion
      • Check for abdominal tenderness/ hepatomegaly/ ascites
      • Examine for bleeding manifestation
      • Tourniquet test (repeat if previously negative or if there is no bleeding manifestation)
  • Investigations:
    • FBC & HCT
    • Renal and liver function tests
    • INR & APTT
    • Dengue serology
    • BFMP
    • Other relevent tests
  • After clinical assessment
    • Day…….fever
    • Temp chart – Febrile phase / Critical phase
        • Hours of defervescence
    • Alarm signals – Yes/No
      • Abdominal pain and vomiting / Restlessness / Cold and clammy extrimities / Altered conscious level / A sudden change from fever to hypothermia
    • Bleeding tendency – Yes/No
    • Evidence of plasma leakage – Yes/No
      • Pleural effusion / Ascites
      • Hemodynamic instability - INCLUDING TACHYCARDIA (PR>90)
      • Increase in HCT
  • Diagnosis :
    • Dengue Haemorrhagic Fever
    • D6 illness
    • Deferversence 12 hours
    • With right pleural effusion and ascites
    • Clinically no alarming signs / bleeding
    • (EXAMPLE)
  •