What is the WHO 2009 classification for dengue and the recommended day‑by‑day management to maintain adequate intravascular volume, monitor for bleeding or organ dysfunction, and avoid fluid overload?

WHO 2009 Dengue Classification and Day-by-Day Management

The WHO 2009 classification divides dengue into three categories—dengue without warning signs, dengue with warning signs, and severe dengue—with management focused on daily monitoring for plasma leakage, judicious fluid resuscitation to prevent shock while avoiding overload, and early recognition of the critical phase (typically days 3-7) when progression to severe disease occurs. 1, 2

WHO 2009 Classification System

The 2009 WHO classification replaced the older DF/DHF/DSS system and stratifies patients into three distinct severity groups 3, 4:

Dengue Without Warning Signs (Group A)

• Fever plus two or more of: nausea, vomiting, rash, headache, retro-orbital pain, myalgia, arthralgia, positive tourniquet test, or leukopenia 2
• No evidence of plasma leakage, hemorrhage, or organ dysfunction 3
• Safe for outpatient management with daily monitoring 5

Dengue With Warning Signs (Group B)

• Any dengue case with one or more warning signs 1:
  • Severe abdominal pain or persistent vomiting 1, 2
  • Mucosal bleeding 1
  • Lethargy or restlessness 1
  • Fluid accumulation (ascites, pleural effusion) 3
  • Liver enlargement >2 cm 3
  • Rising hematocrit concurrent with rapidly falling platelet count 1, 2
• Requires hospitalization for close monitoring 3

Severe Dengue (Group C)

• Severe plasma leakage leading to shock or fluid accumulation with respiratory distress 1, 3
• Severe bleeding requiring transfusion 1
• Severe organ impairment (AST/ALT ≥1000, altered consciousness, heart or other organ failure) 3
• Requires immediate ICU admission 1

Important caveat: The 2009 classification has high sensitivity (71.5%) but lower specificity compared to clinical gestalt, and approximately 75% of cases are classified as having warning signs even though only 2-3% develop plasma leakage 6, 3. This means careful clinical judgment is essential to avoid over-triage.

Day-by-Day Management Algorithm

Days 1-3: Febrile Phase

Outpatient Management (Group A):

• Encourage oral hydration targeting 2,500-3,000 mL daily using water, oral rehydration solutions, cereal-based gruels, soup, or rice water 7, 2
• Avoid soft drinks due to high osmolality 7
• Acetaminophen only for fever and pain; never aspirin or NSAIDs due to bleeding risk 1, 2
• Daily monitoring with complete blood count to track platelet and hematocrit trends 1, 2
• Obtain dengue PCR/NAAT on serum during days 1-7 for diagnostic confirmation 2

Inpatient Monitoring (Group B):

• Daily CBC monitoring to track hematocrit (rising indicates plasma leakage) and platelet count 1, 2
• Maintain oral hydration or initiate IV crystalloid at maintenance rates if unable to tolerate oral intake 1
• Monitor vital signs every 4-6 hours: heart rate, blood pressure, capillary refill, urine output 7
• Watch for progression to severe disease 1

Days 3-7: Critical Phase

This is the highest-risk period for plasma leakage and progression to shock. 1, 2

Key monitoring parameters:

• Rising hematocrit (>20% increase from baseline) signals ongoing plasma leakage and need for fluid resuscitation 2
• Narrowing pulse pressure (<20 mmHg) or hypotension indicates impending shock 7
• Tachycardia, poor capillary refill (>2 seconds), cold extremities, altered mental status, and oliguria are shock indicators 7

Fluid Management for Dengue Shock Syndrome:

• Administer 20 mL/kg isotonic crystalloid (0.9% normal saline or Ringer's lactate) as rapid bolus over 5-10 minutes 1, 7
• Reassess immediately after each bolus for improvement in tachycardia, tachypnea, capillary refill, and mental status 1
• Repeat crystalloid boluses up to 40-60 mL/kg in the first hour if shock persists 1, 7
• Consider colloid solutions (dextran, gelafundin, or albumin) for severe shock with pulse pressure <10 mmHg, as colloids achieve faster shock resolution (RR 1.09) and require less total volume (31.7 vs 40.63 mL/kg) 1

Critical endpoints to target:

• Normal capillary refill time (<2 seconds) 7
• Warm, dry extremities with well-felt peripheral pulses 7
• Return to baseline mental status 7
• Adequate urine output (>0.5 mL/kg/hour in adults) 2
• Stable vital signs 7

Management of refractory shock:

• If shock persists despite 40-60 mL/kg crystalloid in first hour, switch from aggressive fluids to inotropic support rather than continuing fluid boluses 1, 7
• For cold shock with hypotension: titrate epinephrine as first-line vasopressor 1, 7
• For warm shock with hypotension: titrate norepinephrine as first-line vasopressor 1, 7
• Target age-appropriate mean arterial pressure and ScvO2 >70% 1

Bleeding management:

• Blood transfusion indicated for significant bleeding with hemoglobin <10 g/dL if ScvO2 <70% 1
• Platelet transfusion generally not indicated unless active bleeding with severe thrombocytopenia 1

Days 7-10: Recovery Phase

Critical pitfall: Fluid overload during recovery can cause pulmonary edema and respiratory distress 1, 2

Management approach:

• Discontinue IV fluids once patient is hemodynamically stable and tolerating oral intake 1
• After initial shock reversal, judicious fluid removal may be necessary; aggressive shock management followed by fluid removal decreased pediatric ICU mortality from 16.6% to 6.3% 1
• Consider continuous renal replacement therapy (CRRT) if fluid overload >10% develops 1
• Monitor for resolution of plasma leakage: falling hematocrit indicates successful plasma re-expansion 1

Discharge Criteria

Patients can be safely discharged when ALL of the following are met: 2

• Afebrile for ≥48 hours without antipyretics 2
• Resolution or significant improvement of symptoms 2
• Stable hemodynamic parameters for ≥24 hours without support (normal heart rate, blood pressure, capillary refill) 2
• Adequate oral intake 2
• Adequate urine output (>0.5 mL/kg/hour in adults) 2
• Laboratory parameters returning to normal ranges 2

Post-discharge instructions:

• Monitor temperature twice daily 2
• Return immediately if fever ≥38°C on two consecutive readings or any warning signs develop 2

Common Pitfalls to Avoid

The single most dangerous error is administering routine bolus IV fluids to patients with "severe febrile illness" who are NOT in shock—this increases fluid overload and respiratory complications without improving outcomes 1, 7. Reserve aggressive fluid resuscitation exclusively for documented shock.

Other critical pitfalls:

• Failing to recognize the critical phase (days 3-7) when plasma leakage rapidly progresses to shock 1
• Continuing aggressive fluid administration once signs of fluid overload appear (hepatomegaly, pulmonary rales, respiratory distress) 1
• Delaying vasopressor therapy in refractory shock; delays are associated with increased mortality 1
• Using aspirin or NSAIDs, which worsen bleeding tendencies 1, 2
• Relying on blood pressure alone in children, as shock can be present with normal blood pressure 1