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DENGUE FEVER - Comprehensive MD/DNB Pediatrics Review

Senior Professor of Pediatrics & Infectious Diseases | Evidence-Based, Exam-Oriented

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1. DEFINITION AND OVERVIEW

Must Know: ~75% of dengue infections are asymptomatic. Of symptomatic cases, <5% progress to severe dengue. Yet early identification of this minority is the entire clinical challenge.

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2. EPIDEMIOLOGY

Global Burden

• 2024 record year: >14.4 million cases reported to WHO; >52,000 severe cases; >10,000 deaths (WHO 2024)
• 136 countries or territories with current/prior autochthonous transmission
• Cases roughly doubled annually since 2021 - declared one of WHO's 10 threats to global health
• Highest burden: Brazil (Americas), Indonesia, India (South-East Asia)
• All 4 serotypes circulate in Americas; DENV-2 and DENV-3 commonly cause severe disease

Indian Burden (NVBDCP/NCVBDC)

• India is hyper-endemic - all 4 serotypes circulate
• Seasonal peaks: post-monsoon (August-November) and pre-monsoon (May-June) in some regions
• 2024: India among highest reported cases in South-East Asia Region
• Under-reporting is massive - true burden estimated 10-100x reported cases
• States with highest burden: Maharashtra, Kerala, Karnataka, Tamil Nadu, Delhi, Uttar Pradesh
• Children 5-15 years most affected; infants at high risk for severe disease

Exam Pearl: India uses the 1997 WHO (DHF/DSS) classification in official NVBDCP guidelines alongside WHO 2009. Clinicians must know both.

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3. VIROLOGY

Dengue Virus Serotypes (DENV-1 to DENV-4)

• Four antigenically distinct serotypes - all cause dengue but differ in epidemic potential
• DENV-2 and DENV-3: associated with more severe disease in secondary infections
• Fifth putative serotype (DENV-5): reported in 2013 from Malaysia, sylvatic origin - not yet widely recognized clinically

Virus Structure

+-------------------------------------------+
|  Single-stranded (+) sense RNA virus       |
|  Family: Flaviviridae                       |
|  Genus: Orthoflavivirus (formerly Flavivirus)|
|  Genome: ~11 kb                            |
|  Envelope: Icosahedral + lipid bilayer     |
|  Proteins:                                 |
|    Structural: C (capsid), prM, E (envelope)|
|    Non-structural: NS1, NS2A, NS2B, NS3,   |
|      NS4A, NS4B, NS5                       |
|  Key antigen: NS1 (diagnostic target)      |
|  E protein: mediates receptor binding      |
+-------------------------------------------+

• NS1 antigen is shed freely into blood during early infection - basis of NS1 RDT
• E protein is the major target for neutralizing antibodies

Transmission Cycle

Infected human → Aedes aegypti feeds (bloodmeal) 
→ Extrinsic incubation: 8-12 days in mosquito
→ Virus in salivary glands
→ Mosquito bites susceptible human
→ Intrinsic incubation: 3-14 days (typically 4-7 days)
→ Symptomatic or asymptomatic infection
→ Viremic human is infectious to new mosquitoes
  for ~7 days (1-2 days before fever onset + throughout fever)

Vector Biology

Exam Pearl: Aedes mosquitoes bite during daytime - bed nets alone are insufficient; repellents must be used during day. Breeding in stagnant water as small as 5 mL (e.g., bottle caps).

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4. PATHOGENESIS

4.1 Antibody-Dependent Enhancement (ADE)

PRIMARY INFECTION (any serotype):
→ Infection cleared → Lifelong serotype-specific immunity
→ Cross-protective antibodies (last 1-3 years) against other serotypes

SECONDARY INFECTION (different serotype):
→ Pre-existing non-neutralizing heterotypic IgG antibodies 
→ Bind to new serotype virus but cannot neutralize it
→ DENV-antibody complexes bind via Fc receptors 
  to monocytes/macrophages (FcγRII/CD32)
→ ENHANCED viral entry into cells
→ Higher viral load → Amplified immune response → SEVERE DISEASE

4.2 Immune Response

• Innate: Pattern recognition, IFN-α/β production, NK cell activation
• T cells: Cross-reactive T cells from prior infection amplify response - "original antigenic sin"
• Cytokines: TNF-α, IL-2, IL-6, IL-8, IL-10, IFN-γ released in a "storm"
• NS1 protein activates complement and disrupts endothelial glycocalyx

4.3 Plasma Leakage Mechanism

• Transient (24-48 hrs) increase in vascular permeability during critical phase
• Mechanisms:
  1. NS1 antigen disrupts endothelial glycocalyx (direct endothelial damage)
  2. Cytokine-mediated (TNF-α, IL-6, VEGF) endothelial activation
  3. Complement activation (C3a, C5a)
  4. Mast cell degranulation releasing histamine
  5. Platelet-activating factor (PAF)
• Results in plasma leaking into third space (pleural cavity, peritoneum, subcutaneous tissues)
• Key: Leakage is SELECTIVE - plasma proteins leak, causing hemoconcentration

4.4 Cytokine Storm

• Activated T cells and monocytes release massive cytokines
• NS1, NS4B proteins suppress IFN response, prolonging viremia
• IL-10 (anti-inflammatory) paradoxically worsens outcome by impairing viral clearance

4.5 Bleeding Mechanisms

1. Thrombocytopenia (most important):
   • Suppressed megakaryopoiesis (direct viral infection of bone marrow)
   • Peripheral destruction by anti-platelet antibodies (molecular mimicry - DENV NS1 ↔ platelet antigen)
   • Platelet consumption (endothelial damage)
2. Coagulopathy: DIC in severe cases; reduced clotting factors (hepatic dysfunction)
3. Vascular fragility: Capillary damage by cytokines and complement
4. Platelet dysfunction: Functional defect even when count is not very low

4.6 Organ Dysfunction

• Liver: Direct viral infection of hepatocytes + immune-mediated hepatitis; DENV-3 most hepatotropic
• Brain: Viral encephalitis (rare - direct invasion), encephalopathy (metabolic - hyponatremia, hepatic failure, hypoxia)
• Myocardium: Viral myocarditis, bradycardia (dengue "vasovagal" bradycardia also seen)
• Kidney: Hypoperfusion-induced AKI, immune complex glomerulonephritis, rhabdomyolysis
• HLH: Immune dysregulation triggering hemophagocytosis - rare but life-threatening

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5. RISK FACTORS FOR SEVERE DENGUE

Must Know Box:

RISK FACTORS FOR SEVERE DENGUE
================================
Patient-related:
• Secondary dengue infection (MOST IMPORTANT)
• Infants < 1 year (maternal antibodies = ADE)
• Extremes of age
• Obesity (harder to assess plasma leak; risk of fluid overload)
• Pregnancy
• Chronic diseases: DM, sickle cell, asthma, cardiac disease, renal disease, thalassemia
• Immunocompromised (HIV, on steroids)
• Hematological disorders (hemophilia, ITP)

Viral-related:
• DENV-2 and DENV-3 (higher virulence strains)
• High viral load

Serotype-related:
• Secondary infection with heterologous serotype
• DENV-2 secondary after DENV-1 primary (most severe combination)

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6. CLASSIFICATION

6.1 Classical WHO 1997 Classification

Exam Pearl: DSS = DHF Grades III and IV. The 4 criteria for DHF = FEVER, HEMORRHAGIC TENDENCY, THROMBOCYTOPENIA, PLASMA LEAKAGE. All 4 must be present.

6.2 Current WHO 2009 Classification (and WHO 2024 Arboviral Guidelines)

6.3 Indian National (NVBDCP) Classification

• NVBDCP officially uses WHO 1997 (DF/DHF Grades I-IV) system for case classification and reporting
• Clinically, management guidelines now incorporate WHO 2009 triage groups (A, B, C)
• This dual system creates confusion: India reports cases as DHF but manages using Group A/B/C

Comparison Table: WHO 1997 vs WHO 2009

• Actionable (directly guides admission/triage)
• Captures expanded dengue syndrome
• Works in primary care settings
• Better sensitivity for severe outcomes

• "Warning signs" are not specific - overdiagnose severity
• No clear cutoff for lab values (except AST/ALT ≥1000 for organ impairment)
• Less validated in non-Asian settings initially

• Clear, objective criteria
• Well validated in South-East Asia
• Still useful for epidemiological comparison

Recent Guideline Update: WHO 2024 Guidelines for Clinical Management of Arboviral Diseases (covers dengue, chikungunya, Zika, yellow fever) - reaffirms 2009 classification while providing updated fluid management recommendations. PAHO also updated their case definitions in 2024.

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7. CLINICAL FEATURES

The Three-Phase Model

FEBRILE PHASE          CRITICAL PHASE         RECOVERY PHASE
(Days 1-3)             (Days 4-6)              (Days 7-10+)
─────────────────      ───────────────         ──────────────
• Abrupt high fever    • Defervescence          • Reabsorption of
  (39-40°C)           • Plasma leakage           leaked fluid
• Facial flushing      • Hemoconcentration     • Diuresis
• Headache             • Thrombocytopenia nadir • "Isles of white
• Retro-orbital pain   • Warning signs appear     in sea of red"
• Myalgia/arthralgia   • ↑HCT + ↓platelets       (convalescent rash)
• Rash (macular)       • Pleural effusion      • Bradycardia
• Petechiae            • Ascites               • Generalized pruritus
• +ve tourniquet test  • Shock (DSS)           • Fatigue
• Leukopenia           • Bleeding              • Appetite returns
• ↓Platelets begin     • SHOCK IS THE           RISK: Fluid overload
• Positive NS1/PCR       MAIN DANGER             if excess IV given

7.1 Febrile Phase (Days 1-3)

• Sudden onset high fever (often >39°C), may reach 40-41°C
• Characteristic "saddleback" fever pattern in some cases (fever → brief defervescence → return)
• Faget's sign: Relative bradycardia despite high fever (pulse-temperature dissociation)
• Facial flushing, injected conjunctivae, pharyngeal injection
• Rash: Initially flushing, then maculopapular (day 3-4)
• Petechiae on extremities, trunk
• Positive tourniquet test (Rumpel-Leede test): Inflate BP cuff midway between systolic/diastolic for 5 minutes - positive if >10 petechiae/square inch (or >20 in 1 inch² area)
• Leukopenia: WBC often 3,000-5,000/µL; neutropenia + atypical lymphocytosis
• Minor bleeding: epistaxis, gum bleeding, easy bruising

7.2 Critical Phase (Days 3-7, typically Days 4-5)

• Occurs at/around defervescence - MOST DANGEROUS PERIOD
• Rapid plasma leak → hemoconcentration (HCT rises ≥20% from baseline)
• Pleural effusion (right-sided > bilateral) and ascites
• Thrombocytopenia nadir (platelets <20,000-50,000/µL)
• Warning signs manifest (see Section 8)
• Progression to DSS: rapid, weak pulse → narrow pulse pressure (<20 mmHg) → hypotension → profound shock
• Massive bleeding can occur (GI bleed, hematemesis, melena, hematuria)
• Duration of critical phase: 24-48 hours - window for intervention

Common Mistake: Fever breaking does NOT mean the patient is improving. In dengue, defervescence = entry into critical phase. Warn parents explicitly!

7.3 Recovery Phase (Days 7-10+)

• Extravascular fluid reabsorption - risk of fluid overload if too much IV fluid was given
• Diuresis, improved urine output
• Platelet count recovers
• Convalescent rash: "isles of white in a sea of red" - pathognomonic
• Bradycardia (vagal tone)
• Generalized pruritus
• Danger in this phase: Pulmonary edema, CCF from fluid overload

7.4 Age-Wise Clinical Presentation

7.5 Expanded Dengue Syndrome (EDS)

• Neurological: Encephalitis (direct viral invasion), encephalopathy (metabolic), meningitis, myelitis, Guillain-Barré syndrome, acute disseminated encephalomyelitis (ADEM), optic neuritis
• Cardiac: Myocarditis, cardiomyopathy, pericarditis, arrhythmias, AV blocks
• Hepatic: Acute hepatitis, acute liver failure (rare), cholecystitis
• Renal: AKI, glomerulonephritis, nephrotic syndrome
• Musculoskeletal: Rhabdomyolysis, myositis
• Hematological: HLH, aplastic anemia
• Ophthalmological: Dengue maculopathy, uveitis

Exam Pearl: EDS is diagnosed when severe organ involvement occurs WITHOUT evidence of severe plasma leakage. It represents direct viral organotropism.

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8. WARNING SIGNS

Must Know Box:

WARNING SIGNS (WHO 2009) - Mnemonic: "ALARM"
==============================================
A - Abdominal pain (severe, persistent)
L - Lethargy/restlessness (clinical deterioration)
A - Accumulated fluid (pleural effusion, ascites)
R - Rapid decline in platelet + rising HCT
    Retching (persistent vomiting ≥3 episodes/hour)
M - Mucosal bleed
    + Liver enlargement >2 cm

Exam Pearl: Warning signs do NOT equal severe dengue - they predict RISK of severe dengue. A patient with warning signs = Group B2 (hospitalize, monitor, IV fluids).

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9. SEVERE DENGUE

9.1 Severe Plasma Leakage

• Shock (DSS): Rapid, weak, thready pulse; narrow pulse pressure (<20 mmHg); cold extremities; prolonged capillary refill (>2 sec); oliguria
• Massive effusion causing respiratory distress (pleural effusion + ascites)
• Compensated shock: Low pulse pressure with normal systolic BP → treat urgently
• Decompensated/hypotensive shock: Overt hypotension
• HCT rise ≥20% from baseline (e.g., from 35% to 42%+)

9.2 Severe Bleeding

• Clinically significant hemorrhage requiring intervention
• Criteria: Gross hematemesis, massive melena, heavy menorrhagia, intracranial hemorrhage
• Associated with profound thrombocytopenia + DIC + shock
• Note: Spontaneous bleeding from gums/nose alone does not = severe bleeding (unless massive)

9.3 Severe Organ Involvement

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10. LABORATORY DIAGNOSIS

10.1 CBC Interpretation

10.2 Hematocrit Trends

• Normal HCT: Males 40-45%, Females 37-42%, Children 35-40% (age dependent)
• ≥20% rise from baseline: Significant hemoconcentration = plasma leak
• Example: Baseline HCT 35% → rises to 42% = 20% increase → significant
• Falling HCT in shock patient: May indicate massive internal hemorrhage (NOT improvement)
• Serial monitoring: Every 6-12 hours in critical phase; every 2-4 hours if warning signs

Common Mistake: Trusting a single HCT value. Always compare to baseline or prior value. A "normal" HCT of 42% in a child with dengue + shock may still represent 20% rise from their baseline of 35%.

10.3 Platelet Count Significance

• <100,000/µL = significant thrombocytopenia in dengue
• <50,000/µL = monitor closely; admission required
• <20,000/µL = severe; risk of spontaneous hemorrhage
• Platelet nadir: Day 4-7 of illness (typically during critical phase)
• Rate of fall MORE important than absolute value
• Recovery: Platelets begin rising by Day 7-9 (often dramatic rebound in recovery phase)

10.4 Diagnostic Tests Overview

10.5 Investigation Timeline (Diagnostic)

DAYS FROM FEVER ONSET
Day:   0    1    2    3    4    5    6    7    8    9   10   11   12
       |----+----+----+----+----+----+----+----+----+----+----+----|
VIRUS  |████████████████████████|
NS1    |████████████████████████████|
RT-PCR |████████████████████████|
IgM    |                   |████████████████████████████████████
IgG    |     (Primary:             |████████████████████████████
        (Secondary: rises from Day 1-2: |██████████████████████████

CLINICAL:
Febrile|████████████████████|
Critical                   |████████████████|
Platelets ↓↓↓              |↓↓↓↓↓↓↓(nadir)↓|→ recovery
HCT ↑                      |↑↑↑↑↑↑↑↑       |→ normalization

Exam Pearl: NS1 + IgM combination test on a single sample during Days 1-10 achieves >90% sensitivity for dengue diagnosis. This is the recommended diagnostic approach per WHO 2024.

10.6 Primary vs Secondary Dengue Infection

Exam Pearl: IgG/IgM ratio >1.2 on acute sample = primary infection. IgG early + high = secondary. Secondary infections account for majority of DHF/DSS.

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11. DIFFERENTIAL DIAGNOSIS

Exam Pearl: In India, always test for malaria + dengue simultaneously in endemic areas - co-infection is possible and both require specific treatment.

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12. INVESTIGATIONS

12.1 Baseline Investigations (On Admission)

• CBC with differential and platelet count
• Hematocrit
• Blood glucose (hypoglycemia is a complication)
• Dengue NS1 antigen (Days 1-7) ± IgM
• Blood group and cross-match (if severe)
• Electrolytes (Na+, K+, Cl-)
• Liver function tests (AST, ALT, total bilirubin, albumin)
• Serum creatinine, BUN
• Coagulation profile (PT, aPTT, fibrinogen) - if bleeding suspected
• CXR (PA view) - for pleural effusion
• USG abdomen - for ascites, gallbladder edema, hepatomegaly

12.2 Monitoring Investigations

12.3 Serial HCT Interpretation

Serial HCT Interpretation Guide:
==================================
Rising HCT (>20% from baseline)  → Plasma leakage → Increase IV fluids
Stable HCT on fluids             → Adequate hydration → Maintain rate
Falling HCT on fluids (improving)→ Plasma reabsorption → Reduce fluids
Falling HCT in shocked patient   → MASSIVE INTERNAL BLEEDING → Blood transfusion
Rapidly falling HCT + hypotension→ Hemorrhagic shock → EMERGENCY

12.4 Liver Function Tests

• AST/ALT: Rise from Day 3 onwards; usually returns to normal by Day 14-21
• AST > ALT typically (AST also elevated from muscle involvement)
• Mild elevation (<400): Common dengue hepatitis - watchful management
• Severe elevation (≥1000 IU/L): Severe organ impairment criterion - ICU care
• Albumin: Falls with plasma leakage (important to track); hypoalbuminemia worsens edema
• Bilirubin: Mildly elevated in most; high in hepatic dengue

12.5 Coagulation Profile

• Prolonged PT/aPTT: DIC, hepatic dysfunction
• Low fibrinogen (<100 mg/dL): DIC active
• D-dimer elevated: Fibrinolysis in DIC
• Indication: Any patient with active bleeding, suspected DIC, or AST/ALT >1000

12.6 Electrolytes

• Hyponatremia (Na+ <130): Common; causes encephalopathy; occurs from plasma leakage (dilutional) and SIADH
• Hypokalemia: Common; especially during recovery phase (large diuresis)
• Hypocalcemia: Can occur; especially in severe dengue

12.7 Imaging

• Right pleural effusion (most common) - blunting of costophrenic angle
• Bilateral effusions in severe cases
• Cardiomegaly if myocarditis
• Pulmonary edema in fluid overload
• Standing CXR best - even small effusions visible; lateral decubitus can reveal tiny effusions

• Gall bladder wall edema (>3 mm) = early sign of plasma leakage - PATHOGNOMONIC finding in dengue
• Ascites (free fluid in Morrison's pouch, around liver, pelvis)
• Hepatomegaly
• Pleural effusion (bilateral views)
• Helps guide decision for critical phase management
• Can detect leakage before clinical signs appear

Exam Pearl: Gallbladder wall thickening >3 mm on USG is an early marker of plasma leakage in dengue and may appear BEFORE clinical warning signs. Use it proactively in borderline cases.

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13. MANAGEMENT - WHO 2009 / WHO 2024 / NVBDCP GUIDELINES

13.1 Triage System (WHO 2009 Groups A / B / C)

DENGUE TRIAGE
═════════════════════════════════════════════════════════════
GROUP A (Send Home - Outpatient)
─────────────────────────────────
• No warning signs
• Tolerating oral fluids
• Passing urine ≥6 hourly
• Stable vital signs
• No high-risk features (pregnancy, infant, comorbidity, social risk)

GROUP B (Hospitalize for Monitoring/IV Fluids)
──────────────────────────────────────────────
B1: Warning signs ABSENT but high-risk patient
   (infant, elderly, pregnant, obesity, DM, renal disease, 
    unable to tolerate oral fluids)
B2: Warning signs PRESENT
   (any of the 7 warning signs)

GROUP C (Emergency Treatment - ICU/HDU)
────────────────────────────────────────
• Compensated shock
• Hypotensive shock
• Severe organ impairment
• Severe bleeding
• Severe plasma leakage with respiratory distress
═════════════════════════════════════════════════════════════

13.2 Admission Criteria

• Warning signs present
• Platelet <100,000/µL with HCT rising
• Platelet <50,000/µL (any situation)
• Infants, pregnant women
• Social circumstances (unable to follow-up, lives far from hospital)
• Comorbidities
• Signs of organ dysfunction

13.3 Outpatient Management (Group A)

• Paracetamol: 10-15 mg/kg/dose PO q6h (max 4 doses/24 hrs; max 60 mg/kg/day)
• AVOID: Aspirin, NSAIDs (ibuprofen), steroids
• Oral fluids: ORS, coconut water, fresh fruit juices, soups - at least 5 glasses (adults) or weight-appropriate volumes; minimum 200 mL/kg/day in children <20 kg
• Warning signs education: Written instructions to family; return immediately if warning signs develop
• Monitoring: Review daily (or sooner if warning signs)
• Check CBC and HCT at Day 3-5 (critical phase) even if initially stable

13.4 Inpatient Management - Monitoring Schedule

13.5 ICU Indications

• Refractory shock (not responding to 2-3 fluid boluses)
• Severe bleeding requiring blood products
• Respiratory distress / ARDS / need for mechanical ventilation
• AST/ALT ≥1000 with encephalopathy
• Myocarditis with cardiogenic shock
• AKI requiring dialysis
• HLH
• Multi-organ dysfunction syndrome

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14. FLUID MANAGEMENT (MOST IMPORTANT SECTION)

Must Know: Fluid management is the CORNERSTONE of dengue treatment. Inadequate fluids → shock and death. Excessive fluids → pulmonary edema and death. Precision is paramount.

14.1 Principles

1. Fluids are needed only during plasma leakage phase (24-48 hours of critical phase)
2. Use the MINIMUM amount of fluid to maintain adequate tissue perfusion
3. Guide therapy by clinical parameters + serial HCT
4. STOP IV fluids as soon as plasma reabsorption begins (diuresis, clinical improvement, falling HCT)
5. Crystalloids first; colloids only for rescue in refractory shock

14.2 Maintenance Fluid Calculation (Holiday-Segar Formula)

Body Weight          Maintenance Volume (24 hours)
< 10 kg             100 mL/kg/day
10-20 kg            1000 mL + 50 mL/kg for each kg above 10
> 20 kg             1500 mL + 20 mL/kg for each kg above 20

Example: Child 25 kg = 1500 + (5 × 20) = 1500 + 100 = 1600 mL/day
Hourly rate = 1600 ÷ 24 = ~67 mL/hr (approximately 2-3 mL/kg/hr)

14.3 NVBDCP Fluid Regimens by Body Weight

Must Know: NVBDCP uses 4 regimens: R1 (3), R2 (6), R3 (10), R4 (20 mL/kg/hr). Do NOT jump from R2 to R4 directly - step up and step down gradually.

14.4 Types of Fluids

• 0.9% Normal Saline (NS) - most commonly available
• Ringer's Lactate (RL) / Hartmann's solution - preferred (more physiological, balanced, less hyperchloremic acidosis)
• Plasmalyte - balanced solution; evidence from SPLID trial (India, ongoing 2026) comparing to standard therapy

• Dextran 40 or 70
• Hetastarch (HES) - avoid in renal impairment
• Indication: Only when shock persists after 2-3 crystalloid boluses (refractory shock)
• Dose: 10-20 mL/kg over 30-60 minutes, then reassess

Recent Guideline Update (WHO 2024): Balanced crystalloids (Ringer's Lactate, Plasmalyte) preferred over 0.9% NS to avoid hyperchloremic metabolic acidosis. Colloids reserved for refractory shock unresponsive to adequate crystalloid. [PMID 40068930 - 691 children, 7 SE Asian hospitals, 2025: Early appropriate resuscitation associated with better outcomes]

14.5 Stepwise Fluid Algorithm

For Group B WITHOUT Warning Signs:

ORAL ROUTE PREFERRED
↓
If cannot tolerate oral → IV at maintenance rate (R1: 3 mL/kg/hr)
↓
Reassess every 4-6 hours
↓
Monitor: HCT, urine output, vital signs
↓
Stop IV fluids when: oral intake adequate + urine output good

For Group B WITH Warning Signs (Stepwise IV Protocol):

STEP 1: Baseline HCT + start IV isotonic fluid (NS or RL)
        Rate: 5-7 mL/kg/hr for 1-2 hours
        ↓
STEP 2: Reassess clinically
        Improved → Reduce to 3-5 mL/kg/hr for 2-4 hours
        ↓
STEP 3: Reassess again
        Improved → Reduce to 2-3 mL/kg/hr for 2-4 hours
        ↓
STEP 4: Continue 2-3 mL/kg/hr until hemodynamically stable + tolerating oral
        ↓
STEP 5: Stop IV fluids when no leakage, adequate urine, HCT stable

14.6 Management Based on HCT Changes

14.7 Recognition of Fluid Overload

• Respiratory distress, increased respiratory rate
• New/worsening pulmonary edema (crepitations)
• Increasing hepatomegaly (tender)
• New pleural effusion / ascites (but note: these also occur from dengue itself - distinguish by timing)
• Periorbital/facial edema
• Hypertension in non-hypotensive dengue

• Falling HCT DESPITE deterioration (dilutional)
• Hyponatremia worsening
• CXR: Pulmonary venous congestion, Kerley B lines, bat-wing pattern

1. Stop IV fluids immediately
2. Elevate head of bed (if no shock)
3. Oxygen supplementation
4. Furosemide: 0.1-0.5 mg/kg/dose IV (ONLY if: HCT is falling/normal, BP stable, in recovery phase, urine output was previously good)
5. DO NOT give furosemide in shock - will worsen hypovolemia
6. Monitor urine output - target 0.5-1 mL/kg/hr

14.8 Special Fluid Situations

• Use weight-based calculations carefully
• Harder to assess plasma leakage clinically
• Prone to hyponatremia and hypoglycemia - add dextrose (D5NS or D5RL)
• More frequent reassessment (every 1-2 hours in critical phase)
• Include breastfeeding in fluid intake assessment

• Use IDEAL body weight for fluid calculations (not actual body weight)
• Risk of underestimating plasma leakage
• Higher risk of respiratory complications and fluid overload
• Lower threshold for ICU admission

• Use SMALLER volumes (start with 5 mL/kg bolus rather than 10-20)
• More frequent reassessment
• Avoid rapid boluses
• May need invasive monitoring

• Titrate fluids to urine output carefully
• Risk of fluid overload and electrolyte imbalance
• Early dialysis threshold should be lower
• Avoid nephrotoxic agents

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15. SHOCK MANAGEMENT

15.1 Compensated Shock (Group C - Narrow Pulse Pressure <20 mmHg, normal systolic BP)

COMPENSATED SHOCK ALGORITHM
═════════════════════════════
Baseline HCT → Start ISOTONIC CRYSTALLOID (NS or RL)
Bolus: 10-20 mL/kg over 15-30 minutes
           ↓
    Reassess at 15-30 min
    (Pulse, BP, pulse pressure, capillary refill, urine output)
           ↓
   IMPROVED?
    YES → Reduce to 10 mL/kg/hr × 1-2 hr
          → Reduce to 7 mL/kg/hr × 2 hr
          → Reduce to 5 mL/kg/hr × 4 hr
          → Reduce to 3 mL/kg/hr
          → Continue until stable, step down by HCT
    NO  → Repeat bolus 10-20 mL/kg over 15-30 min
          Check HCT
          If HCT RISING → More plasma leakage → Colloid (10-20 mL/kg)
          If HCT FALLING → Hemorrhage → Packed RBC (10 mL/kg)

15.2 Hypotensive Shock (Group C - Overt Hypotension)

HYPOTENSIVE SHOCK ALGORITHM
═════════════════════════════
IMMEDIATE:
→ IV access (2 large-bore IV lines)
→ Oxygen (high-flow face mask/NRM)
→ Rapid fluid bolus: 20 mL/kg isotonic crystalloid over 15 minutes
→ Check HCT + blood group/cross match
           ↓
    Reassess at 30 min
    IMPROVED → Reduce rate stepwise (as above)
    NOT IMPROVED (HCT HIGH) → Switch to COLLOID 10-20 mL/kg over 30 min
                               OR Repeat crystalloid 10 mL/kg
    NOT IMPROVED (HCT LOW) → Suspect HEMORRHAGE
                              → Packed RBC 10 mL/kg
                              → Consider FFP 10 mL/kg + Cryoprecipitate
                              → Crossmatch urgently

15.3 Refractory Shock

REFRACTORY SHOCK (No response to 40-60 mL/kg total crystalloid + colloid)
══════════════════════════════════════════════════════════════════════════
• ICU admission MANDATORY
• Rule out:
  - Massive internal hemorrhage (HCT falling despite fluids)
  - Myocarditis / Cardiogenic shock (echo: poor contractility)
  - Severe metabolic acidosis (pH <7.2)
  - Tension pneumothorax / Pericardial tamponade
  - HLH

• Add VASOPRESSORS if still hypotensive after adequate fluid resuscitation:
  - Norepinephrine: 0.05-0.3 mcg/kg/min (vasodilatory shock)
  - Dopamine: 5-20 mcg/kg/min (alternative)
  
• Check:
  - Calcium (correct hypocalcemia)
  - Blood glucose (correct hypoglycemia)
  - Electrolytes (correct severe hyponatremia)
  
• Mechanical ventilation if respiratory failure
• Dialysis if AKI
• Inotropes (dobutamine 5-20 mcg/kg/min) if cardiogenic component
• ECMO (last resort): Limited evidence in dengue shock

Common Mistake: Giving fluid bolus in cardiogenic shock due to dengue myocarditis will worsen the patient. Always evaluate cardiac function (echo or clinical signs) before large fluid boluses in refractory shock.

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16. PLATELET TRANSFUSION

16.1 Latest Evidence

• WHO 2024, AABB 2025 guidelines, and multiple systematic reviews consistently show prophylactic platelet transfusion does NOT reduce bleeding risk or mortality in dengue thrombocytopenia
• [PMID 40440268] AABB/ICTMG International Clinical Practice Guidelines 2025: Do not give prophylactic platelet transfusions for non-bleeding dengue patients
• [PMID 41624243] 2026 review: Platelet transfusion in tropical thrombocytopenia - clinical characteristics and management in resource-limited settings: supports conservative approach

16.2 Current Indications for Platelet Transfusion

16.3 When Platelet Transfusion is NOT Indicated

Must Know Box:

PLATELET TRANSFUSION IS NOT INDICATED WHEN:
=============================================
✗ Platelets >20,000 with NO active bleeding (prophylactic)
✗ Platelets 10,000-20,000 with NO severe bleeding
✗ Minor mucosal ooze (epistaxis, petechiae) without hemodynamic compromise
✗ Pre-operative "just in case" without evidence-based threshold
✗ To "prevent" bleeding based on platelet count alone
✗ Platelet count recovering (rising trend documented)
✗ Recovery phase (platelet rebound expected)

HARM FROM UNNECESSARY TRANSFUSION:
• Fluid overload (each unit adds ~200-250 mL)
• Transfusion reactions (febrile non-hemolytic, allergic, TRALI)
• Alloimmunization
• Increased infection risk
• Cost (especially in resource-limited settings)

16.4 FFP, Cryoprecipitate, and Blood Transfusion

Exam Pearl: In dengue, NEVER give platelet transfusion to prevent bleeding prophylactically - this is one of the most tested exam points and one of the most common clinical errors. Platelets will fall to single digits and recover spontaneously in dengue. Transfuse ONLY for uncontrolled active bleeding.

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17. MANAGEMENT OF COMPLICATIONS

17.1 Massive Bleeding

• Identify and treat source (GI endoscopy if stable, not in shock)
• Packed RBC: 10 mL/kg (to maintain Hb >8-10 g/dL in actively bleeding patient)
• FFP + Cryoprecipitate (DIC)
• Platelets ONLY if active uncontrolled hemorrhage + count <50,000
• Tranexamic acid (antifibrinolytic) - used in some centers for massive hemorrhage; limited dengue-specific evidence
• Vitamin K: 1 mg/kg IV (max 10 mg) if hepatic coagulopathy
• Avoid excessive fluids during active hemorrhage

17.2 Dengue Hepatitis

• Mild-moderate hepatitis: Supportive (rest, avoid hepatotoxic drugs)
• Avoid paracetamol if AST/ALT >3-5× normal (use minimum dose or avoid)
• N-acetylcysteine: Consider if acute hepatic failure pattern
• Coagulopathy management: Vitamin K, FFP if active bleeding
• Severe hepatic failure: ICU, avoid sedatives, monitor for encephalopathy, glucose, ammonia

17.3 Encephalopathy

• Causes: Hyponatremia (most common), hepatic encephalopathy, hypoglycemia, cerebral hypoperfusion
• Management: Correct underlying cause
  • Hyponatremia: Correct slowly (3% saline 1-2 mL/kg for severe symptomatic); avoid rapid correction
  • Hypoglycemia: 10% dextrose 2 mL/kg IV bolus
  • Cerebral edema: Mannitol 0.25-0.5 g/kg (controversial in dengue)
  • Seizures: IV benzodiazepine (diazepam 0.3 mg/kg or lorazepam)
  • Avoid hepatotoxic drugs

17.4 Encephalitis (True Viral Encephalitis)

• Rare; direct DENV invasion of CNS
• CSF: pleocytosis (usually lymphocytic), elevated protein, DENV RNA on PCR
• MRI: T2/FLAIR signal abnormalities in basal ganglia, thalamus, temporal lobes
• Treatment: Supportive; no specific antiviral approved
• Dexamethasone: Use controversial in dengue encephalitis - some centers use 0.15 mg/kg q6h for cerebral edema with encephalitis
• IVIG: Anecdotal reports; not standard

17.5 Myocarditis

• Presents as: Persistent tachycardia/bradycardia, hypotension, poor myocardial contractility, arrhythmias
• ECG: AV blocks, T-wave inversions, prolonged QT, arrhythmias
• Troponin elevated, BNP elevated
• Echo: Reduced LVEF, wall motion abnormalities
• Management:
  • Restrict fluids (cardiogenic shock - DO NOT give large fluid boluses)
  • Inotropes: Dobutamine 5-10 mcg/kg/min if reduced EF
  • Anti-arrhythmics as needed (amiodarone, not beta-blockers if hypotensive)
  • Temporary pacemaker if complete heart block
  • IVIG and steroids: Anecdotal use; not evidence-based

17.6 Acute Kidney Injury (AKI)

• Causes: Hypoperfusion (most common), rhabdomyolysis, hemolysis, immune-mediated, direct viral
• KDIGO AKI staging (Cr rise, urine output criteria)
• Management:
  • Adequate fluid resuscitation (target urine output 0.5-1 mL/kg/hr)
  • Avoid nephrotoxic drugs (gentamicin, NSAIDs, contrast)
  • Electrolyte correction (hyperkalemia)
  • Early renal replacement therapy (CVVH preferred in hemodynamically unstable)
  • Peritoneal dialysis: Alternative in resource-limited settings

17.7 ARDS

• Causes: Fluid overload (most common), direct pulmonary involvement, secondary infection
• Distinguish from dengue-related pleural effusion
• Management:
  • Lung-protective ventilation: Tidal volume 6 mL/kg ideal body weight
  • PEEP 5-10 cm H2O
  • Fluid restriction (careful balance with shock management)
  • Prone positioning for severe ARDS
  • Avoid oxygen toxicity

17.8 Hemophagocytic Lymphohistiocytosis (HLH)

• Rare but life-threatening dengue complication
• HLH-2004 diagnostic criteria (5 of 8):
  1. Fever
  2. Splenomegaly
  3. Cytopenias (≥2 cell lines)
  4. Hypertriglyceridemia (>265 mg/dL) and/or hypofibrinogenemia (<150 mg/dL)
  5. Hemophagocytosis on BM biopsy
  6. Low/absent NK cell activity
  7. Ferritin >500 ng/mL (typically >10,000 in HLH)
  8. Elevated soluble CD25 (sIL-2R)
• HScore also useful
• Management: Treat underlying dengue + Dexamethasone 10 mg/m²/day ± etoposide (in refractory HLH); IVIG sometimes used
• Ferritin >10,000 is a red flag

Exam Pearl: Very high ferritin (>10,000 ng/mL) in dengue should raise suspicion for HLH. Dengue-associated HLH may have better outcomes than primary HLH if dengue is recognized and treated promptly.

17.9 Expanded Dengue Syndrome

• As detailed in Section 7.5
• Neurological EDS: Treat like viral encephalitis + dengue management
• Eye complications: Ophthalmology referral; some respond to steroids
• Each organ complication managed on its own merit plus dengue-specific fluid management

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18. SPECIAL SITUATIONS

18.1 Infants

• Higher risk of severe disease (maternal IgG → ADE)
• Clinical assessment harder (cannot verbalize symptoms)
• Warning signs may present differently (irritability, refusal to feed, lethargy)
• Fluid management: Include breastfeeds in volume calculation
• Higher risk of hypoglycemia - monitor blood glucose every 4-6 hours
• Use D5NS or D5RL (add dextrose to IV fluids)
• Threshold for admission LOWER than older children

18.2 Neonates

• Vertical transmission: Especially high risk when maternal dengue in last week before delivery
• Presentations: Fever, thrombocytopenia, liver dysfunction, hydrops fetalis (rare)
• NS1 may be positive; IgM unreliable (maternal IgM confounds)
• Management: Supportive; blood transfusion + platelets if severe hemorrhage
• Monitor for withdrawal of maternal antibody protection

18.3 Adolescents

• Clinical presentation similar to adults
• Obesity increasingly common → adjust fluid calculations to ideal body weight
• Mental health impact of prolonged dengue illness (depression, fatigue)
• DENV-2 secondary infection especially problematic in this age group

18.4 Pregnancy

• Risk of preterm labor, placental abruption, fetal death
• Vertical transmission to fetus (~20%); risk highest with dengue near delivery
• Maternal dengue managed similarly but:
  • Platelet threshold for transfusion may be higher (obstetric bleeding risk)
  • Monitor fetal well-being
  • Multidisciplinary care (obstetrics + pediatrics/neonatology)
  • Mode of delivery: Vaginal delivery preferred; Cesarean only for obstetric indication
  • Postpartum: High risk of hemorrhage if thrombocytopenic at delivery
  • Breastfeeding: Generally safe; dengue virus rarely detected in breast milk

18.5 Immunocompromised Children

• HIV, post-transplant, on chemotherapy, on long-term steroids
• May have atypical/prolonged course
• Higher risk of bacterial co-infection
• NS1 may be negative in HIV with CD4 <200 (impaired NS1 production)
• Dengue IgM may be falsely negative (impaired humoral immunity) - rely more on NS1 and PCR
• Management: Standard dengue management; adjust immunosuppression if possible

18.6 Children with Hematological Disorders

• Sickle cell disease: Dengue can precipitate vaso-occlusive crisis; transfusion thresholds may differ
• ITP: Difficult to distinguish from dengue thrombocytopenia; fever + NS1 helps
• Thalassemia: Baseline anemia complicates HCT monitoring; use % change from patient's known baseline
• Hemophilia: High bleeding risk; coordinate with hematology; factor replacement + dengue fluid management
• Leukemia patients: High fever may mask infection; always test for dengue during dengue season

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19. DISCHARGE CRITERIA

Must Know Box:

DISCHARGE CRITERIA (WHO 2009 + NVBDCP)
=========================================
Clinical:
✓ Afebrile for at least 24-48 hours WITHOUT antipyretics
✓ Improvement in clinical status (alert, active)
✓ Good appetite (tolerating adequate oral intake)
✓ Urine output adequate (urinating normally)
✓ No respiratory distress
✓ No abdominal pain
✓ No further bleeding

Laboratory:
✓ Platelet count rising and trending toward ≥50,000/µL
  (do NOT wait for platelets to reach 100,000 - discharge if rising trend)
✓ Hematocrit stable at patient's own baseline
✓ No evidence of ongoing plasma leakage

Duration:
• At least 24-48 hours of observation after critical phase resolution
• Usually Day 7-9 of illness (if uncomplicated severe dengue)
• Day 3-5 (if Group B with warning signs resolved)

Common Mistake: Keeping patients hospitalized until platelets reach 100,000/µL. If platelets are rising (e.g., 30,000 → 50,000 → 80,000 trend) and clinical criteria are met, discharge is SAFE. Platelet rebound in recovery phase is dramatic and reliable.

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20. FOLLOW-UP

• Review at 24-48 hours post-discharge (check CBC to confirm platelet recovery)
• Return to school/activity: After full recovery (typically 1-2 weeks from illness onset)
• Avoid NSAIDs, aspirin, anticoagulants for at least 2 weeks post-discharge
• Follow up LFTs if elevated at discharge (repeat at 4-6 weeks)
• Post-dengue fatigue syndrome: Common; reassurance; no specific treatment
• Advise on prevention and warning signs for future dengue episodes
• Inform about risk of severe disease in subsequent heterologous infection

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21. PREVENTION

21.1 Vector Control

• Source reduction (most effective): Eliminate breeding sites
  • Remove/empty/cover all water containers weekly
  • Dispose of old tyres, plastic containers, flower pot saucers
  • Cover overhead water tanks, water storage vessels
• Biological control:
  • Bacillus thuringiensis israelensis (Bti) - larval control
  • Gambusia fish (mosquito fish) in large water bodies
  • Wolbachia-infected mosquitoes: Aedes aegypti infected with Wolbachia bacterium reduces DENV replication in mosquitoes → population-level dengue reduction (deployed in parts of Indonesia, Colombia, Australia - dramatic success)
• Chemical control:
  • Larval: Temephos (abate) in drinking water containers
  • Adult: Space spraying (fogging) with pyrethrin/malathion - INDOOR RESIDUAL SPRAYING not effective for Aedes
• Sterile Insect Technique (SIT): Release of sterile male mosquitoes
• Genetically modified mosquitoes (OX513A): Male mosquitoes carry dominant lethal gene - offspring die before breeding

21.2 Community Measures

• India's "10-minute anti-dengue day" every Friday - check for stagnant water
• Community mobilization - "Search and Destroy" breeding sites
• Drainage of stagnant water in public spaces
• Surveillance and reporting of cases
• School-based programs

21.3 Personal Protection

• Repellents: DEET (10-30% for children >2 months), Picaridin, IR3535, oil of lemon eucalyptus
• Protective clothing (long sleeves, pants) especially during peak biting hours (morning, late afternoon)
• Permethrin-treated clothing
• Screened windows and doors
• Air conditioning
• Bed nets (for daytime sleeping infants especially)

21.4 Vaccines

CYD-TDV (Dengvaxia, Sanofi Pasteur)

• Type: Live recombinant, chimeric yellow fever-dengue tetravalent vaccine
• Schedule: 3 doses at 0, 6, 12 months
• Approved ages: 9-45 years in endemic countries; 9-16 years by US FDA (2019)
• Critical caveat: ONLY FOR SEROPOSITIVE INDIVIDUALS (prior dengue infection confirmed)
  • Seronegative recipients have INCREASED risk of severe dengue after vaccination (ADE mechanism)
  • Pre-vaccination serology screening required
• Efficacy (seropositive): ~85% against severe dengue, ~77% overall
• NOT approved in India by DCGI as of 2024; not in IAP/NVBDCP schedule
• Exam Pearl: Dengvaxia controversy - Philippines halted program in 2017 after reports of death in vaccinated seronegative children

TAK-003 / Qdenga (Takeda)

• Type: Live attenuated tetravalent dengue vaccine; all 4 serotypes backbone from DENV-2
• Schedule: 2 doses, 3 months apart
• Approved ages: 4-60 years (EU approval 2022-2023); Indonesia, Brazil, Argentina, UK, Thailand
• Key trial: TIDES Phase 3 trial - 20,099 children aged 4-16 years in Asia and Latin America
• Efficacy:
  • Overall: ~73% against virologically confirmed dengue
  • Against dengue hospitalization: ~84%
  • Against severe dengue: ~90%
  • Works in BOTH seronegative and seropositive individuals (unlike Dengvaxia)
  • Limitation: Lower efficacy against DENV-3; DENV-4 not well represented in trial
  • Small signal of increased DENV-3 hospitalization risk in seronegative (WHO monitoring this)
• WHO recommendation (2024): Recommend for countries with high transmission; pre-vaccination serology NOT required; best impact in high-seroprevalence settings (>80%)
• India status: Not yet approved by DCGI as of mid-2026; under review

Recent Guideline Update: WHO SAGE (2024) recommended TAK-003/Qdenga for use in children aged ≥6 years in settings with high dengue burden. India has not yet introduced any dengue vaccine into the national immunization schedule. IAP awaits DCGI approval. [PMID 40432095 - Wilder-Smith, Vaccines 2025; PMID 40195054 - systematic review adolescent vaccines 2025]

Butantan-DV (Butantan Institute, Brazil)

• Single-dose tetravalent vaccine
• Phase 3 trial (Brazil): High efficacy in seropositive; limited in seronegative
• Not yet approved globally

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22. RECENT UPDATES (2021-2026)

22.1 WHO 2024 Arboviral Guidelines

• Major update: WHO published "Guidelines for Clinical Management of Arboviral Diseases" (2024) covering dengue, chikungunya, Zika, yellow fever jointly
• Reaffirms 2009 classification
• Emphasizes balanced crystalloids over 0.9% NS
• Colloids only for refractory shock
• Prophylactic platelet transfusion STRONGLY discouraged
• Emphasizes oral hydration wherever possible

22.2 Epidemiology Updates

• 2024 was a record year for dengue globally: >14.4 million cases, >10,000 deaths
• Climate change expanding Aedes mosquito range to temperate zones (Europe, North America)
• Unprecedented outbreaks in Europe (Croatia, France, Italy) with local transmission

22.3 Recent Platelet Transfusion Evidence

• AABB/ICTMG 2025 Clinical Practice Guideline [PMID 40440268]: Strong recommendation against prophylactic platelet transfusion in dengue
• Multiple RCTs and meta-analyses confirm NO benefit and POTENTIAL HARM from prophylactic platelet transfusion in dengue thrombocytopenia
• Threshold recommendations: Transfuse ONLY for active, uncontrolled severe bleeding

22.4 Updated Fluid Management

• SPLID Trial (India, 2026 - protocol published [PMID 41923109]): Comparing Plasmalyte vs standard NS in dengue shock syndrome in children - results awaited
• SE Asian multicenter study (691 children, 2025 [PMID 40068930]): Confirmed that early and appropriate fluid resuscitation reduces mortality; both crystalloid types comparable
• Emphasis on avoiding fluid overload - associated with worse outcomes in critical phase
• WHO 2024: Titrate fluids to clinical endpoints, not fixed formulas

22.5 New Diagnostic Modalities

• Rapid NS1+IgM combination tests: High sensitivity (>90%) in single sample
• DENV NS1 biosensors: Point-of-care, CRISPR-based, nanomaterial tests under development
• Portable RT-PCR: NAAT platforms (GeneXpert) providing same-day dengue serotyping
• Machine learning models: Predicting severe dengue from Day 1-3 clinical/lab parameters
• USG gallbladder wall thickening: Validated as early plasma leakage marker even before clinical warning signs

22.6 Vaccine Updates

• Qdenga: Approved in EU (2022), UK, Indonesia, Brazil, Thailand, Argentina, Japan
• WHO SAGE 2024: Recommended for countries ≥6 years in high-burden settings
• India: No dengue vaccine approved/in NIS as of mid-2026; under DCGI review
• Post-marketing surveillance: Ongoing for DENV-3 signal in Qdenga seronegative recipients
• New candidates: mRNA-based dengue vaccines (Moderna, BioNTech) in early Phase 1 trials

22.7 Emerging Antivirals Under Research

• No specific antiviral approved for dengue as of 2026
• Promising candidates:
  • Balapiravir (R1626): Nucleoside analogue - reduced viremia but no clinical benefit in trials
  • Celgosivir: α-glucosidase inhibitor; Phase 2 trials (negative results)
  • Imatinib: Tyrosine kinase inhibitor; reduces plasma leakage in animal models; under investigation
  • Monoclonal antibodies: Cross-reactive anti-DENV broadly neutralizing mAbs (AZD1613, others) - Phase 1-2
  • NS5 polymerase inhibitors, NS3 helicase/protease inhibitors: Preclinical/early Phase
  • WHO PADO 2025 (Paediatric Drug Optimization Exercise): Identified antiviral drugs for dengue as a priority for pediatric formulation development
• Key challenge: Small therapeutic window (viremic phase only 5-7 days; most patients present late)

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23. MD/DNB PRACTICAL AND VIVA QUESTIONS WITH MODEL ANSWERS

1. Compensated or decompensated shock does not improve after 2-3 adequate crystalloid boluses (total ~30-40 mL/kg)
2. HCT remains elevated (suggesting ongoing plasma leakage rather than hemorrhage)
3. Continued shock despite adequate crystalloid The rationale is that colloids have larger molecules that stay in the intravascular space longer during active plasma leakage, providing more sustained hemodynamic support.

1. There is clinical fluid overload (pulmonary edema, respiratory distress)
2. BP is stable (not in shock)
3. HCT is at or below baseline (indicating plasma has reabsorbed)
4. Urine output was previously adequate NEVER give furosemide during the critical phase or in shock - it will worsen hypovolemia and precipitate organ failure.

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24. HIGH-YIELD EXAM PEARLS

TOP EXAM PEARLS - DENGUE
=========================

1. Dengue = Flavivirus, 4 serotypes (DENV 1-4); ~75% asymptomatic
2. Aedes aegypti bites DAYTIME - not protected by nighttime bed nets alone
3. DHF = ALL FOUR: Fever + Hemorrhage + Thrombocytopenia + Plasma leakage
4. Warning signs: ALARM = Abdominal pain, Lethargy/restlessness, 
   Accumulated fluid, Rapid platelet fall + HCT rise, Mucosal bleed 
   (+ persistent Retching/vomiting + liver >2 cm)
5. Defervescence = entry into critical phase (NOT improvement!)
6. Critical phase lasts only 24-48 hours
7. Convalescent rash = "isles of white in sea of red" - recovery phase
8. Gallbladder wall >3 mm = early plasma leakage sign on USG
9. HCT ≥20% rise from baseline = significant plasma leakage
10. Falling HCT in shock = HEMORRHAGE (not improvement); give pRBC
11. Prophylactic platelet transfusion = WRONG (proven in multiple RCTs)
12. Furosemide ONLY in recovery phase with fluid overload, not in shock
13. NS1 positive = Days 1-7; IgM positive from Day 3-5 onward
14. Early IgG on acute sample = secondary infection → higher risk severe
15. AST/ALT ≥1000 = severe organ impairment (criterion for severe dengue)
16. ADE = mechanism of secondary severe dengue + Dengvaxia harm
17. Dengvaxia = seropositive only; Qdenga = seropositive + seronegative
18. Balanced crystalloids (RL) preferred over 0.9% NS (hyperchloremia)
19. Colloids ONLY for refractory shock after adequate crystalloids
20. NVBDCP uses 1997 classification (DF/DHF/DSS); clinically use 2009

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25. IMPORTANT TABLES

Table 1: WHO 2009 Classification

Table 2: Warning Signs

Table 3: Differential Diagnosis Summary

Table 4: Investigation Timeline

Table 5: Fluid Management Algorithm (Summary)

Table 6: Shock Management Algorithm

Table 7: Platelet Transfusion Indications

Table 8: Discharge Criteria

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26. FLOWCHARTS (ASCII)

Flowchart 1: Dengue Diagnosis Algorithm

FEVER IN ENDEMIC AREA
         │
         ▼
Dengue suspected?
(Headache, retro-orbital pain, myalgia, rash, 
 leukopenia, +ve tourniquet test)
         │
         ▼
     DAYS 1-5?              DAYS 5-10?
         │                      │
    NS1 antigen             IgM antibody
    ± RT-PCR                ± IgG
    ± IgM                        │
         │                       │
    ┌────┴────┐             ┌────┴────┐
  Positive  Negative      Positive  Negative
    │         │              │         │
 DENGUE   Consider        DENGUE    Consider
CONFIRMED  alternate       PROBABLE  alternate
           diagnosis       (confirm) diagnosis
                                │
                     CBC + HCT for severity
                          assessment

Flowchart 2: Triage Algorithm

DENGUE PATIENT ARRIVES
         │
         ▼
Any warning signs?
(Abdominal pain, persistent vomiting, fluid accumulation,
 mucosal bleeding, lethargy, liver >2 cm, 
 rapid platelet ↓ + HCT ↑)
         │
    YES  │  NO
   ┌─────┘  └─────┐
   ▼              ▼
GROUP B2        Tolerating oral fluids?
(Admit + IV)         │
                YES  │  NO
               ┌─────┘  └─────┐
               ▼              ▼
           High-risk?      GROUP B1
           (infant, pregnant,  (Admit +
            elderly, comorbid)  IV fluids)
               │
          YES  │  NO
         ┌─────┘  └──────┐
         ▼               ▼
       GROUP B1         GROUP A
       (Admit)         (Outpatient)
         │
    Any severe features?
    (Shock, severe bleeding,
     organ impairment)
         │
         ▼
       GROUP C
      (Emergency/ICU)

Flowchart 3: Fluid Management Algorithm

DENGUE + FLUID DECISION
         │
    Can tolerate oral?
     YES   │   NO (or warning signs)
      │    │       │
    ORS  Group A  IV FLUIDS REQUIRED
    +    → Home       │
   oral               ▼
                  Check HCT (baseline)
                  Start NS or RL
                       │
                 Warning signs only?
                 Rate: 5-7 mL/kg/hr × 1-2 hr
                       │
                  Reassess
               Improved? ──YES──► Reduce to 3-5 mL/kg/hr
                  │                     │
                  NO                 Reduce to 2-3 mL/kg/hr
                  │                     │
              SHOCK?                  Stop IV when:
            ┌──┴───┐                 oral OK + urine OK
            │      │                 + HCT stable
     HCT  HIGH  HCT LOW
          │       │
       Colloid  pRBC
    10-20 mL/kg 10 mL/kg

Flowchart 4: Shock Management Algorithm

DENGUE SHOCK
      │
      ▼
Compensated?         Hypotensive?
(Narrow PP           (Low BP)
 normal systolic)
      │                  │
Crystalloid           Crystalloid
10-20 mL/kg           20 mL/kg
bolus ×15-30 min      RAPID ×15 min
      │                  │
      ▼                  ▼
   IMPROVED?           IMPROVED?
   YES → Stepdown      YES → Stepdown
   NO ↓                NO ↓
      │                  │
   Check HCT          Check HCT
   HIGH ── COLLOID     HIGH ── COLLOID
   LOW  ── pRBC +      LOW  ── pRBC + FFP
           coagulation
      │                  │
   STILL NOT IMPROVED?
         │
         ▼
    REFRACTORY SHOCK
    → ICU + Vasopressors
    → Rule out: hemorrhage, myocarditis, HLH
    → Norepinephrine 0.05-0.3 mcg/kg/min
    → Dobutamine if cardiogenic
    → Dialysis if AKI
    → Ventilate if ARDS

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27. CLINICAL CASE SCENARIOS WITH MANAGEMENT

Case 1: Typical Dengue with Warning Signs

• HCT rise: (40-34)/34 × 100 = 17.6% (approaching significant)
• Warning signs: Abdominal pain + persistent vomiting + rising HCT + platelets 55,000
• Group B2 → Admit

1. Admit; IV access; baseline investigations (CBC, LFT, electrolytes, NS1+IgM, USG)
2. NS or RL at 5-7 mL/kg/hr (for 8 kg child... wait, he's 8 years - use weight ~25 kg): Rate = 5-7 × 25 = 125-175 mL/hr for 1-2 hours
3. Strict I/O monitoring; urine output hourly
4. Repeat HCT in 2-4 hours
5. Paracetamol 10-15 mg/kg q6h PO or PR (max 4 doses/day)
6. USG for gallbladder wall, effusions
7. If HCT rises further → increase rate; if HCT stable and clinical improvement → stepdown

Case 2: Dengue Shock Syndrome

• HCT rise: (52-36)/36 × 100 = 44% - massive plasma leakage
• Hypotensive shock (Decompensated DSS)
• Group C - Emergency

1. ABCDE approach
2. High-flow O2 via non-rebreather mask
3. TWO large bore IV lines
4. Rapid crystalloid bolus: 20 mL/kg NS or RL over 15 minutes (weight ~18-20 kg = 360-400 mL)
5. Baseline investigations: HCT, blood group/cross-match, glucose, electrolytes
6. Reassess at 30 minutes:
   • Improved → reduce to 10 mL/kg/hr, then step down
   • Not improved + HCT still high → Switch to COLLOID (dextran 40) 10-20 mL/kg
7. Check blood glucose (hypoglycemia correction: 10% dextrose 2 mL/kg)
8. ICU admission
9. Urinary catheter for strict hourly output
10. Serial HCT every 2 hours

Case 3: Dengue with Myocarditis

• Refractory shock but with cardiogenic component
• Low LVEF + bradycardia + persistent shock after fluids = DENGUE MYOCARDITIS
• Do NOT give more fluid boluses

1. STOP further fluid boluses (will worsen pulmonary edema)
2. ICU admission
3. Dobutamine 5-10 mcg/kg/min IV infusion (inotrope + vasodilator - increases CO)
4. If bradycardia causing shock: Atropine 0.02 mg/kg IV; consider temporary pacing if complete heart block
5. Continuous ECG monitoring
6. Troponin, CK-MB, BNP
7. Echo daily
8. Careful fluid restriction
9. Norepinephrine ONLY if vasodilatory shock confirmed

Case 4: Dengue + Thrombocytopenia Dilemma

• Recovery phase (afebrile, Day 7, eating well)
• Platelet count very low but NO bleeding
• Expected platelet rebound in recovery phase

1. DO NOT transfuse platelets (no active bleeding, recovery phase, platelets expected to rise)
2. Educate family: Dengue thrombocytopenia is self-limiting; platelet will recover in 2-5 days
3. Avoid all trauma, injections, NSAIDs
4. Strict bleeding precautions: soft toothbrush, avoid vigorous nose blowing
5. Monitor daily CBC
6. Discharge criteria met otherwise → discharge with daily outpatient follow-up
7. Return immediately if: any active bleeding (gum bleed, hematemesis, unusual bruising with hemodynamic change)

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28. MNEMONICS FOR RAPID REVISION

DENGUE (Overview)

D - Daytime-biting Aedes (aegypti primary vector)
E - Endemic in tropics; four serotypes (DENV 1-4)
N - NS1 early marker (Day 1-7)
G - Gradual thrombocytopenia + hemoconcentration
U - Usually self-limiting; 24-48 hr critical window
E - Enhance (ADE) in secondary infections = severe disease

WARNING SIGNS - "ALARM + LV"

A - Abdominal pain (severe, persistent)
L - Lethargy / restlessness
A - Accumulated fluid (ascites, pleural effusion)
R - Rapid platelet fall + rising HCT
M - Mucosal bleeding
+
L - Liver enlargement >2 cm
V - Vomiting (persistent, ≥3 episodes/hr)

DHF (1997 WHO) - "FHTP"

F - Fever (2-7 days, high grade)
H - Hemorrhagic tendency (at least +ve tourniquet test or petechiae)
T - Thrombocytopenia (<100,000/µL)
P - Plasma leakage (HCT rise ≥20% or pleural effusion/ascites)

WHEN TO GIVE COLLOID - "RICO"

R - Refractory shock (no response to 2-3 crystalloid boluses)
I - Isotonic crystals failed
C - Continuing plasma leak (HCT still HIGH in shock)
O - Only after adequate crystalloid trial

DISCHARGE CRITERIA - "FAPU"

F - Fever-free ≥24-48 hours (no antipyretics)
A - Appetite returning + Adequate oral intake
P - Platelets rising (trend toward ≥50,000)
U - Urine output normal
(+ no bleeding, no respiratory distress, stable HCT)

SEVERE DENGUE - "3 S's"

S1 - Severe Plasma leakage → Shock or respiratory distress
S2 - Severe Bleeding (clinician-assessed significant hemorrhage)
S3 - Severe organ involvement (AST/ALT ≥1000, impaired consciousness, heart failure)

FLUIDS TO AVOID IN DENGUE - "SAD"

S - Steroids (not indicated for fluid management)
A - Aspirin/NSAIDs (increase bleeding risk)
D - Dextrose-only (hypotonic - worsens hyponatremia; avoid plain D5W as sole resuscitation fluid)

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29. SUMMARY OF ONE-LINERS FOR VIVA AND UNIVERSITY EXAMINATIONS

1. Dengue is caused by 4 serotypes of Orthoflavivirus dengue (DENV 1-4), transmitted by Aedes aegypti mosquitoes, biting during daytime.
2. ADE (Antibody-Dependent Enhancement) explains why secondary dengue infections are more severe - non-neutralizing IgG from prior infection facilitates viral entry into macrophages via Fc receptors.
3. NS1 antigenemia is detectable from Day 1-7; IgM from Day 3-5; early IgG indicates secondary dengue with higher risk of severe disease.
4. The three phases of dengue are Febrile (Days 1-3), Critical (Days 3-6 around defervescence), and Recovery - the critical phase lasts only 24-48 hours.
5. Defervescence (fever breaking) in dengue is NOT a sign of improvement - it marks entry into the critical phase when plasma leakage and shock can occur.
6. WHO 2009 classifies dengue as: (1) Dengue ± warning signs, and (2) Severe dengue - used for clinical triage into Groups A (home), B (admit), C (emergency).
7. NVBDCP/India officially uses WHO 1997 classification (DF, DHF Grades I-IV, DSS) for case reporting; Groups A/B/C for clinical management.
8. Warning signs (ALARM-LV) indicate RISK of progression to severe dengue - they are NOT severe dengue themselves.
9. DHF requires ALL 4 criteria: Fever + Hemorrhagic manifestation + Thrombocytopenia (<100,000) + Plasma leakage (HCT rise ≥20% or clinical effusion/ascites).
10. HCT rise ≥20% from baseline is the laboratory marker of significant plasma leakage in dengue.
11. Gallbladder wall thickening >3 mm on ultrasound is an early sign of plasma leakage - may appear before clinical warning signs.
12. Fluid management in dengue uses isotonic crystalloids (Ringer's Lactate preferred); NVBDCP regimens R1 (3), R2 (6), R3 (10), R4 (20) mL/kg/hr for stepwise management.
13. Colloids are reserved ONLY for refractory shock not responding to adequate crystalloid therapy.
14. Furosemide is ONLY indicated in the recovery phase for fluid overload with stable BP and good baseline urine output - NEVER in shock or active critical phase.
15. Prophylactic platelet transfusion has NO role in dengue - proven by multiple RCTs and the AABB 2025 international guideline - transfuse ONLY for severe uncontrolled active bleeding.
16. Dengvaxia (CYD-TDV) is ONLY for seropositive individuals (prior dengue confirmed) - seronegative recipients face INCREASED risk of severe dengue due to vaccine-induced ADE.
17. Qdenga (TAK-003) is approved for ages ≥4 years in seronegative and seropositive individuals; WHO SAGE 2024 recommends for high-transmission settings; not yet in India's NIS.
18. 2024 was a record year for global dengue with >14 million cases and >10,000 deaths, driven by climate change, urbanization, and travel.
19. HLH complicating dengue: suspect with ferritin >10,000 + cytopenias + splenomegaly; treat with dexamethasone ± etoposide.
20. No specific antiviral is approved for dengue as of 2026 - management remains entirely supportive with precise fluid therapy.

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• Red Book 2021: Report of the Committee on Infectious Diseases, American Academy of Pediatrics - Dengue section, pp. 520-525
• Harrison's Principles of Internal Medicine, 22E (2025, McGraw Hill), Viral Hemorrhagic Fever section
• WHO Guidelines for Clinical Management of Arboviral Diseases (dengue, chikungunya, Zika, yellow fever), 2024
• NVBDCP/NCVBDC Clinical Guidelines on Management of DF/DHF/DSS, Ministry of Health and Family Welfare, Government of India
• PAHO Algorithms for Clinical Management of Dengue Patients, 2024
• Tayal A, Kabra SK, Lodha R. Management of Dengue: An Updated Review. Indian J Pediatr. 2023;90(2):168-177
• Metcalf RA et al. Platelet Transfusion: 2025 AABB and ICTMG International Clinical Practice Guidelines. JAMA. 2025 [PMID 40440268]
• Wilder-Smith A, Cherian T, Hombach J. Dengue Vaccine Development and Deployment into Routine Immunization. Vaccines. 2025 [PMID 40432095]
• Trieu HT et al. Fluid resuscitation strategy outcomes from dengue shock syndrome - 691 children, 7 SE Asian hospitals. BMJ Glob Health. 2025 [PMID 40068930]
• Paranã VC et al. Risk factors for severe dengue in Latin America: Meta-analysis. Trop Med Int Health. 2024 [PMID 38263345]

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Final Note to MD/DNB Residents: Dengue management is deceptively simple in concept but requires continuous bedside vigilance. The two cardinal mistakes that kill dengue patients are: (1) Too little fluid during plasma leakage = prolonged shock = organ failure, and (2) Too much fluid = pulmonary edema in the recovery phase = respiratory failure. Master the timing, dosing, and stopping of IV fluids, and you master dengue management. Good luck in your examinations!