Version 1.0 — Published July 2026
Quick Answer
Dengue is the single highest-yield monsoon-season tropical illness on NEET PG — the NS1/IgM window, WHO 2009 classification, warning signs, the fluid ladder, and platelet transfusion rules recur across every paper. A 28-year-old urban male with day-5 fever, retro-orbital headache, myalgias, macular rash, petechiae, mild epistaxis, HR 110, BP 100/70, platelets 68,000, rising haematocrit needs an 8-step approach:
- Recognise the pattern — day 3-7 fever with retro-orbital headache, myalgias, rash, and bleeding signs in monsoon season = dengue until proven otherwise
- Send NS1 plus IgM combo — NS1 covers days 1-7, IgM from day 5; a negative NS1 late in illness does NOT rule out dengue
- Rule out the Indian tropical mimics — malaria (thick and thin smear or RDT), leptospirosis (water exposure, conjunctival suffusion, myalgia in calves), scrub typhus (find the eschar), chikungunya (arthritis), typhoid (blood culture)
- Classify by WHO 2009 — this patient has warning signs (rising HCT with falling platelets, mucosal bleeding) → admit for IV fluid therapy
- Watch the critical phase — days 3-7 at or just after defervescence; plasma leak, shock, DIC
- Fluid ladder — Ringer lactate 5-7 mL/kg/hr titrated to urine output 0.5 mL/kg/hr; step down as improvement occurs; total IV fluids 24-48 hours
- Do NOT transfuse platelets prophylactically — indications are platelets less than 10,000 (no bleed) OR less than 20,000 with active bleeding OR less than 50,000 pre-procedure
- Monitor — HCT and platelets every 6 hours during critical phase, hourly urine output, capillary refill, pulse pressure, sensorium
The case
A 28-year-old previously healthy male software engineer is brought to the medicine emergency of a tertiary hospital in Bengaluru in mid-July by his housemate with 5 days of high, spiking fever peaking at 40 degrees Celsius. The fever started abruptly on day 1 with severe retro-orbital headache worsened by eye movement, generalised myalgias especially in the lumbar and calf muscles ("break-bone fever"), and small-joint arthralgias of the hands.
He works long hours in an air-conditioned office in Whitefield, walks the 800 m to and from his shared flat every evening, and his neighbourhood has had three confirmed dengue cases in the past two weeks. Two colleagues were admitted last week with similar symptoms. The society's water tanks were last cleaned 40 days ago; construction rubble with stagnant water pools sits at the plot next door.
Over the past 24 hours he has noticed a generalised macular rash on the trunk and limbs — non-itchy, blanching, sparing the face and palms. Faint petechiae appeared on the forearms this morning. Two hours before presentation he had mild epistaxis from the left nostril, stopping spontaneously after 10 minutes of pinch pressure. He also reports mild abdominal discomfort in the right upper quadrant and has vomited twice today — first food, then bile-tinged fluid.
He has taken paracetamol 500 mg every 6 hours for 5 days and one dose of ibuprofen on day 2 (borrowed from a housemate — a red flag for gastric bleeding risk). No self-prescribed antibiotics. No known drug allergy. Non-smoker, occasional alcohol.
Feeding history — poor appetite, taking sips of water and coconut water; passed urine 4 times today (last void 4 hours ago, small volume, concentrated).
On examination — appears unwell, flushed, mildly dehydrated. Alert and oriented. Temperature 39.4, pulse 110/min regular, BP 100/70 (pulse pressure 30 mmHg — narrower than his usual pre-illness 40 mmHg), RR 20/min, SpO2 98 percent on room air, capillary refill 2 seconds, warm peripheries.
Skin — generalised macular blanching erythematous rash on the trunk, back, and thighs; sparing the face and palms; faint petechiae clustered on both forearms; dried blood at the left nasal vestibule. Positive tourniquet test — after inflating the sphygmomanometer to a point midway between systolic and diastolic for 5 minutes, more than 15 petechiae appear in a 2.5 cm square below the antecubital fossa.
HEENT — bilateral conjunctival injection with retro-orbital tenderness on palpation; oropharynx unremarkable, no exudate, no ulcers; no lymphadenopathy.
Cardiovascular — pulse regular, mild tachycardia, no murmur, JVP normal.
Respiratory — clear vesicular breath sounds bilaterally, no crackles, no pleural rub.
Abdomen — soft, mild right hypochondrial tenderness, no palpable hepatomegaly (edge just at the costal margin), no splenomegaly, no ascites on percussion, bowel sounds normal.
CNS — alert, no meningism, no focal deficit.
Musculoskeletal — tender calf muscles bilaterally, tender lumbar paraspinals; no joint swelling; no eschar found on careful search of the axilla, groin, and other warm folds (an eschar would strongly favour scrub typhus).
The admitting resident recognises the pattern, sends urgent labs, and starts IV maintenance fluids while waiting for results. Working diagnosis: suspected dengue fever, day 5, with warning signs (mucosal bleeding, mild abdominal pain, vomiting).
Initial assessment and the time-critical principle
The single most important principle in this case is that the critical phase of dengue starts at defervescence, typically days 3-7, and that plasma leak, shock, and DIC all cluster in this window. A patient whose fever is settling on day 5 but who develops a rising haematocrit alongside a falling platelet count is on the cusp of the critical phase and must be admitted for IV fluid therapy — waiting for shock to declare is too late.
A — Airway: patent.
B — Breathing: RR 20/min, SpO2 98 percent, no distress.
C — Circulation: compensated — HR 110, BP 100/70 with narrow pulse pressure 30 mmHg is a soft sign of early shock; capillary refill 2 seconds; warm peripheries; the narrow pulse pressure (less than 20 mmHg would be shock) needs vigilant monitoring.
D — Disability: AVPU alert.
E — Exposure: monsoon-season urban living, mosquito breeding sites adjacent, cluster of similar cases.
Tier 1 investigations (immediate)
- CBC — Hb 15.5 g/dL (raised from his baseline 14.2 — supports haemoconcentration from plasma leak), WBC 3,200 per microlitre with lymphocytosis (leucopenia is typical of dengue), platelets 68,000 per microlitre (marked thrombocytopenia — normal 150,000-450,000), haematocrit 45 percent (rising from documented pre-illness baseline of 40 percent — an approximate 12 percent rise, meeting the WHO warning-sign criterion of rising HCT with falling platelets)
- Peripheral blood smear — normocytic normochromic RBCs, no malaria parasites seen on thick and thin smear, atypical lymphocytes present
- Rapid malaria antigen test (P. falciparum HRP-2 plus P. vivax LDH) — negative
- NS1 antigen rapid test — positive
- Dengue IgM ELISA — positive (crossed the day-5 threshold)
- Dengue IgG — negative (suggests primary infection; secondary would have raised IgG early)
- LFT — AST 132, ALT 96 U/L (mildly raised — classic hepatitis pattern of dengue), bilirubin 1.1, albumin 3.6 g/dL, total protein 6.8
- Renal — creatinine 1.0, urea 34, Na 136, K 4.1, normal
- Coagulation — PT 14 s, INR 1.2, aPTT 38 s (both mildly prolonged), fibrinogen 240 mg/dL (borderline low — DIC watch), D-dimer 2,800 ng/mL (raised)
- Blood culture — sent, pending (rules out typhoid, sepsis)
- Widal — negative
- Leptospira IgM MAT — sent (given monsoon context)
- Scrub typhus IgM — sent
- Urine routine — specific gravity 1.028 (concentrated), 2+ blood on dipstick without RBCs on microscopy (myoglobinuria consistent with myositis), no proteinuria, no casts
- CXR — normal (baseline; will monitor for pleural effusion in critical phase)
- USG abdomen — gallbladder wall thickening 5 mm (an early sign of plasma leak — the sonographic hallmark of dengue plasma leak), trace right pleural effusion, no ascites, liver and spleen normal size
Interpretation: confirmed dengue (NS1 plus IgM both positive) with WHO 2009 warning signs — rising HCT with falling platelets, mucosal bleeding (epistaxis), abdominal pain, persistent vomiting, and an early sonographic sign of plasma leak (gallbladder wall thickening).
The diagnostic and classification workflow
NEET PG tests the WHO 2009 classification heavily, together with the diagnostic-test windows and the warning-sign list.
WHO 2009 dengue classification
| Category | Criteria | Management |
|---|
| Dengue without warning signs | Fever plus 2 of: nausea/vomiting, rash, aches, positive tourniquet, leucopenia; NO warning sign | Home — oral fluids, paracetamol, daily platelet and HCT check, warning-sign counselling |
| Dengue with warning signs | Abdominal pain, persistent vomiting, clinical fluid accumulation (ascites, effusion), mucosal bleeding, lethargy or restlessness, hepatomegaly greater than 2 cm, rising HCT with falling platelets | Admit — IV crystalloid ladder, 6-hourly HCT and platelets, close monitoring |
| Severe dengue | Severe plasma leak (shock — DSS, respiratory distress from fluid accumulation), severe bleeding, severe organ involvement (ALT/AST greater than 1000, altered mental state, cardiac or other organ failure) | HDU or ICU — aggressive fluid resuscitation, blood products, organ support |
Warning signs mnemonic — AVMBLHR
- A — Abdominal pain or tenderness
- V — persistent Vomiting
- M — Mucosal bleeding (epistaxis, gum bleed, haematuria, menorrhagia)
- B — clinical fluid accumulation (Bulging abdomen with ascites, Basal pleural effusion)
- L — Lethargy or restlessness
- H — Hepatomegaly greater than 2 cm
- R — Rising HCT concurrent with a Rapid drop in platelet count
Dengue serology timeline
| Test | Window | Notes |
|---|
| NS1 antigen | Days 1-7 (peak days 1-4) | Sensitivity 85-95 percent early, drops after defervescence |
| IgM ELISA | Day 5 onwards, positive for 2-3 months | Combined with NS1 as the standard NVBDCP first-line |
| IgG ELISA | After day 14 in primary; day 2-3 in secondary (very high titre) | Rising titre confirms secondary infection |
| RT-PCR | Days 1-5 | Reference standard; research use only |
Differential diagnosis in Indian monsoon-season febrile thrombocytopenia
| Diagnosis | Distinguishing features | Confirmation |
|---|
| Dengue | Retro-orbital headache, myalgia, macular rash, petechiae, mild epistaxis, WBC low or normal | NS1 plus IgM |
| Malaria | Cyclical fever, splenomegaly, anaemia; falciparum with cerebral, renal, ARDS | Thick and thin smear, RDT |
| Leptospirosis | Water or mud exposure, conjunctival suffusion, calf myalgia, jaundice, AKI (Weil) | MAT, IgM ELISA |
| Scrub typhus | Rural or peri-urban, painless eschar, regional LN, responds to doxycycline | IgM ELISA, Weil-Felix OX-K |
| Chikungunya | Severe small-joint arthritis persisting for months, often coexists with dengue | IgM ELISA, RT-PCR |
| Typhoid | Sustained stepwise fever, relative bradycardia, rose spots | Blood culture, Widal |
| Viral haemorrhagic fever (KFD, CCHF) | Endemic area, occupational exposure | Reference lab serology |
| Sepsis with DIC | Hypotension, multi-organ dysfunction, positive culture | Blood culture, coagulation panel |
Critical phase pathophysiology
The critical phase begins at defervescence (typically day 3-7) and lasts 24-48 hours. Plasma leak — driven by cytokine-mediated endothelial dysfunction — moves fluid from the intravascular space into third spaces (pleural effusion, ascites, gallbladder wall oedema). This produces a rising haematocrit (haemoconcentration) with a paradoxically normal or low blood pressure and narrowing pulse pressure (compensated shock). If unrecognised, this progresses to decompensated shock (DSS), DIC, ARDS, myocarditis, hepatitis with liver failure, and dengue encephalopathy. Recovery (reabsorption) begins 24-48 hours later — over-transfused patients drown in reabsorbed fluid.
Diagnosis
Primary dengue infection, day 5, with WHO 2009 warning signs — mucosal bleeding (epistaxis), abdominal pain, persistent vomiting, and rising HCT with falling platelets, plus early sonographic plasma-leak signs (gallbladder wall thickening and trace pleural effusion) — for hospital admission, IV crystalloid ladder, 6-hourly HCT and platelet monitoring, and warning-sign vigilance for progression to severe dengue.
Management — the fluid ladder, monitoring, and transfusion rules
The treatment principle in dengue is judicious isotonic crystalloid titrated to urine output and haemodynamics, avoiding both under-resuscitation (shock) and over-resuscitation (pulmonary oedema during reabsorption).
The fluid ladder
Febrile phase (before warning signs):
- Oral rehydration only if tolerating — coconut water, ORS, rice water, buttermilk
- If unable to drink or vomiting: IV maintenance at approximately 2 mL/kg per hour (roughly 100 mL/hr in a 60 kg adult)
- Paracetamol 500 mg every 6 hours for fever — maximum 4 g/day; watch for hepatotoxicity given LFT derangement
- Avoid NSAIDs, aspirin, and steroids — bleeding and hepatotoxicity risk
- Avoid IM injections (bleeding risk)
Warning signs — critical phase:
- Start isotonic crystalloid (Ringer lactate preferred over 0.9 percent saline for the balanced electrolyte profile) at 5-7 mL/kg per hour for 1-2 hours
- Titrate to urine output 0.5 mL/kg per hour, stable pulse pressure at least 20 mmHg, and warm peripheries
- Step down to 3-5 mL/kg per hour for 2-4 hours if the patient improves
- Step down further to 2-3 mL/kg per hour and consider oral trial when the patient improves further
- Total IV fluid duration in the critical phase is typically 24-48 hours — beyond this, plasma leak has usually reversed and continued fluids cause pulmonary oedema
Compensated shock (narrow pulse pressure less than 20 mmHg, cool peripheries, prolonged CRT):
- Crystalloid at 5-10 mL/kg per hour for 1-2 hours, reassess
- If improving, step down as above
Decompensated shock (hypotension, weak pulse):
- 20 mL/kg crystalloid bolus over 15 minutes, then reassess
- If persistent shock after 2-3 crystalloid boluses, switch to a colloid — dextran 40 or 6 percent HES 130/0.4 at 10-20 mL/kg
- If still refractory, consider blood transfusion for occult haemorrhage (paradoxically falling HCT during ongoing shock — a red flag for haemorrhage)
Transfusion rules
Platelet transfusion is not indicated for isolated thrombocytopenia. The Singapore 2017 trial and multiple observational cohorts confirm that prophylactic platelet transfusion does not reduce bleeding, does not accelerate recovery, and increases fluid overload risk.
Indications:
- Platelet count less than 10,000 per microlitre with no bleeding but high-risk patient (elderly, comorbidities, on antiplatelets)
- Platelet count less than 20,000 per microlitre with any active bleeding (mucosal, GI, urinary, menstrual)
- Platelet count less than 50,000 per microlitre pre-procedure or pre-delivery
- Persistent bleeding with a mixed haemostatic defect (add FFP and cryoprecipitate for DIC)
Blood transfusion (PRBC):
- Suspected significant bleeding with a falling haematocrit during the critical phase
- Persistent shock despite adequate crystalloid and colloid resuscitation
Monitoring during the critical phase
- HCT and platelets every 6 hours — the single most important monitoring parameter
- Hourly urine output — aim for 0.5-1 mL/kg per hour
- Pulse, BP, pulse pressure, capillary refill — every 1-2 hours
- Mental state — restlessness and lethargy are red flags
- Repeat USG at 24-48 hours if plasma leak signs progress
- Repeat CXR if respiratory distress develops
Discharge criteria (WHO)
- Afebrile at least 48 hours without antipyretics
- Improvement in clinical status (appetite, sense of wellbeing, urine output)
- Platelet count rising above 50,000 per microlitre
- Stable haematocrit
- No respiratory distress from effusion or ascites
- At least 2-3 days from resolution of shock
Complications — acute, critical, and convalescent
Acute febrile phase (days 1-3)
- Severe headache, myalgia, hepatitis (mild ALT/AST rise)
- Dehydration from fever, vomiting, and poor intake
Critical phase (days 3-7)
- Plasma leak, dengue shock syndrome (DSS)
- DIC and severe haemorrhage
- Acute liver injury — ALT/AST greater than 1000; occasional fulminant hepatic failure
- Dengue encephalopathy — reduced GCS, seizures; multifactorial (hepatic, hyponatraemia, cerebral oedema)
- Myocarditis and cardiac dysfunction — raised troponin
- Acute kidney injury — pre-renal from hypovolaemia; occasional intrinsic
- Acute respiratory distress syndrome — from plasma leak, fluid overload, or both
Convalescent phase (days 7-14)
- Post-dengue fatigue for 2-4 weeks
- Reabsorption of third-space fluid — watch for pulmonary oedema in over-resuscitated patients
- Convalescent macular rash ("islands of white in a sea of red" — spared skin surrounded by petechial rash)
- Depression, mood changes
Long-term
- Post-dengue chronic fatigue and myalgia for weeks
- Rare — persistent thrombocytopenia, immune-mediated cytopenias
- Secondary infection with a heterologous serotype carries higher DHF/DSS risk — antibody-dependent enhancement
India-specific considerations
- NVBDCP — the National Vector Borne Disease Control Programme runs national surveillance; sentinel hospital reporting is mandatory; DHF/DSS notification is required
- Monsoon and post-monsoon peaks — July to November is the peak transmission window across most of India; south India has a bimodal pattern
- Aedes aegypti biology — daytime biter, prefers clean stagnant water in urban containers; peri-domestic; unlike Anopheles it thrives in cities
- Community-level control — dry-day campaigns, coolers/water tanks emptied weekly, larvicidal Bti or temephos in unused reservoirs, fogging during outbreaks (kills adult vector but not larval)
- Tetravalent dengue vaccine TAK-003 (Qdenga, Takeda) rollout is expanding globally in 2025-2026; India regulatory approval is under review; Dengvaxia (Sanofi CYD-TDV) is restricted to seropositive individuals aged 9-45 due to seronegative safety signal
- Antibody-dependent enhancement (ADE) — a second dengue infection with a different serotype (DENV-1 to DENV-4) produces cross-reactive non-neutralising antibodies that facilitate viral uptake into monocytes and macrophages, increasing DHF/DSS risk
- Outbreak management — line list, source reduction, IEC (information, education, communication), fever screening in schools and offices
- Comorbidity concerns — diabetes and hypertension are the two most common Indian comorbidities and both worsen dengue outcomes; steroid stress and NSAID use before diagnosis complicate 15-20 percent of adult admissions
- Referral thresholds — district hospitals typically manage warning-sign dengue; severe dengue with DSS, ARDS, hepatic failure, or encephalopathy needs referral to a tertiary centre with HDU/ICU, blood bank, and dialysis
How NEET PG tests dengue
Eight recurring patterns.
Pattern 1 — The diagnostic test window question: Which test in dengue on day 3 of fever? NS1 antigen (positive from day 1 to day 7, peak days 1-4). On day 10? IgM ELISA. Combined NS1 plus IgM covers the entire window.
Pattern 2 — The warning signs list question: Which of the following is a WHO warning sign in dengue? Rising HCT with falling platelet count (also abdominal pain, persistent vomiting, mucosal bleeding, lethargy, hepatomegaly greater than 2 cm, clinical fluid accumulation).
Pattern 3 — The critical-phase timing question: When does plasma leak occur? Days 3-7 of illness, typically at or just after defervescence. Duration 24-48 hours.
Pattern 4 — The fluid rate question: First-line IV fluid in dengue with warning signs? Isotonic crystalloid (Ringer lactate) at 5-7 mL/kg per hour titrated to urine output 0.5 mL/kg per hour. Total duration 24-48 hours.
Pattern 5 — The platelet transfusion question: Indication for platelet transfusion in dengue? Platelets less than 10,000 per microlitre with no bleeding OR less than 20,000 per microlitre with active bleeding OR less than 50,000 pre-procedure. Prophylactic transfusion is NOT recommended.
Pattern 6 — The differential question: Dengue vs leptospirosis in a monsoon patient with fever and myalgia? Leptospirosis has water or mud exposure, conjunctival suffusion, prominent calf-muscle myalgia, jaundice, and acute kidney injury (Weil disease). Dengue has retro-orbital headache, rash, and thrombocytopenia with rising HCT.
Pattern 7 — The severe dengue question: Definition of severe dengue? Severe plasma leak with shock or respiratory distress from fluid accumulation, OR severe bleeding, OR severe organ involvement (ALT/AST greater than 1000, altered mental state, cardiac or other organ failure).
Pattern 8 — The ADE question: Why is secondary dengue more severe? Antibody-dependent enhancement — cross-reactive non-neutralising antibodies from the first infection facilitate viral uptake into monocytes and macrophages during infection with a heterologous serotype.
High-yield one-liners:
- Dengue is a flavivirus (DENV-1 to DENV-4) transmitted by Aedes aegypti (day-biting, urban, clean-water breeder)
- NS1 antigen days 1-7; IgM from day 5; IgG after day 14 in primary and early in secondary
- WHO 2009 3-tier classification — without warning signs, with warning signs, severe
- Critical phase days 3-7 at defervescence — plasma leak, shock, DIC
- Gallbladder wall thickening on USG is an early plasma-leak sign
- Isotonic crystalloid (Ringer lactate) at 5-7 mL/kg per hour; step down as improvement occurs
- Total IV fluid duration 24-48 hours — over-resuscitation causes reabsorption pulmonary oedema
- Prophylactic platelet transfusion is NOT recommended
- Avoid NSAIDs, aspirin, steroids, and IM injections in dengue
- Antibody-dependent enhancement drives severe secondary dengue
- Convalescent rash — "islands of white in a sea of red"
- Discharge when afebrile 48 hours, platelets rising above 50,000, stable HCT, no distress
Frequently Asked Questions
Which diagnostic tests confirm dengue and how are they timed against the day of illness?
Dengue diagnostic testing is time-window driven. NS1 antigen is the earliest positive test, detectable from day 1 to day 7 of fever with peak sensitivity 85-95 percent between days 1-4; it drops sharply after defervescence. IgM ELISA becomes positive from day 5 and remains detectable for 2-3 months, so it covers the late febrile and early convalescent phases. IgG appears after day 14 in primary dengue and much earlier (from day 2-3) in secondary dengue where it also reaches very high titres. The Indian national programme (NVBDCP) recommends the combined NS1 plus IgM rapid test as the standard for suspected dengue at first contact because a positive on either arm confirms the diagnosis in the appropriate window. RT-PCR for dengue viral RNA is the reference standard for days 1-5 but is limited to research and outbreak surveillance because of cost. A single tourniquet test showing more than 10 petechiae per 2.5 cm square in an inflated-cuff area is supportive but not diagnostic. NEET PG most commonly tests the NS1 window of days 1-7, the IgM window from day 5, and the fact that a negative NS1 late in illness does not rule out dengue if IgM is positive.
What are the WHO 2009 dengue classification categories and how do the warning signs guide management?
The WHO 2009 classification replaced the older DF/DHF/DSS grading with a 3-tier system tied directly to management. (1) Dengue without warning signs — fever plus 2 of nausea/vomiting, rash, aches, positive tourniquet test, leucopenia, or any warning sign; manage at home with oral fluids, paracetamol only (avoid NSAIDs and aspirin), daily platelet and HCT monitoring, and clear return-precaution advice. (2) Dengue with warning signs — abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation (ascites, pleural effusion), mucosal bleeding, lethargy or restlessness, hepatomegaly greater than 2 cm, and laboratory increase in HCT concurrent with a rapid drop in platelet count; admit for IV fluid therapy and monitoring during the critical phase. (3) Severe dengue — severe plasma leak leading to shock (DSS) or fluid accumulation with respiratory distress, severe bleeding, or severe organ involvement (ALT/AST greater than 1000, impaired consciousness, cardiac or other organ failure); manage in high-dependency or intensive care with aggressive fluid resuscitation, blood products, and organ support. NEET PG tests the warning-sign list heavily — the mnemonic AVMBLHR (Abdominal pain, Vomiting, Mucosal bleeding, Bleeding sites, Lethargy, Hepatomegaly, Rising HCT with falling platelets) is a useful anchor.
How is fluid resuscitation ladder-titrated in dengue with warning signs and shock?
The dengue fluid ladder is one of the most testable protocols in tropical medicine. In the febrile phase manage oral hydration only unless the patient cannot tolerate. Once warning signs appear or the patient enters the critical phase (days 3-7, typically at defervescence), start isotonic crystalloid (Ringer lactate or 0.9 percent saline) at 5-7 mL/kg per hour for 1-2 hours, titrated to urine output at 0.5 mL/kg per hour and stable haemodynamics. Step down to 3-5 mL/kg per hour for 2-4 hours and further to 2-3 mL/kg per hour if the patient improves. Total duration of IV fluids should not exceed 24-48 hours because plasma leak reverses spontaneously and continued aggressive fluids cause pulmonary oedema — a major cause of preventable death. For compensated shock (narrow pulse pressure less than 20 mmHg, cool peripheries, prolonged capillary refill) start crystalloid at 5-10 mL/kg per hour. For decompensated shock (hypotension) give a 20 mL/kg crystalloid bolus over 15 minutes, then reassess. If shock persists after 2-3 crystalloid boluses, switch to a colloid (dextran 40 or 6 percent HES 130/0.4) at 10-20 mL/kg. Blood transfusion is indicated for suspected or overt haemorrhage with a falling haematocrit (paradoxically) rather than a rising one. Once diuresis is established at 0.5-1 mL/kg per hour, taper fluids rapidly to avoid overload.
When is platelet transfusion indicated in dengue and why is prophylactic transfusion contraindicated?
Prophylactic platelet transfusion for isolated thrombocytopenia in dengue is explicitly not recommended by the WHO 2009 guideline, the Indian NVBDCP protocol, and multiple large RCTs (including the Singapore 2017 trial) — it does not reduce bleeding risk, does not accelerate platelet recovery, and increases the risk of fluid overload and transfusion reactions. The indications for platelet transfusion in dengue are (1) platelet count less than 10,000 per microlitre with no bleeding but the patient at high risk (elderly, comorbidities, on antiplatelets), (2) platelet count less than 20,000 per microlitre with any active bleeding including significant mucosal bleeding, and (3) platelet count less than 50,000 per microlitre in a patient going to surgery or delivery. The pathophysiology of bleeding in dengue is multifactorial — thrombocytopenia is one factor, but platelet dysfunction, vascular fragility, DIC, and hepatic dysfunction with reduced clotting factor synthesis all contribute; simply raising the platelet count does not fix the mixed haemostatic defect. NEET PG tests both the numeric thresholds and the anti-prophylactic-transfusion principle.
What are the important differential diagnoses of an Indian patient with monsoon-season fever and thrombocytopenia?
The Indian tropical-medicine acute febrile illness plus thrombocytopenia differential is a high-yield NEET PG cluster. (1) Dengue — retro-orbital headache, myalgia, macular rash, petechiae, mild epistaxis, WBC normal or low, LFT mildly raised, NS1 or IgM positive. (2) Malaria — cyclical fever (tertian for P. vivax, tertian for P. falciparum, quartan for P. malariae), splenomegaly, anaemia, thick and thin peripheral blood smear or rapid diagnostic test positive; falciparum is the killer with cerebral, renal, and multi-organ involvement. (3) Leptospirosis — water or mud exposure (farmers, sewer workers, monsoon flooding), conjunctival suffusion, myalgia especially calf muscles, jaundice, acute kidney injury (Weil disease), MAT or IgM ELISA positive. (4) Scrub typhus — rural or peri-urban exposure, eschar (a painless punched-out ulcer at the mite-bite site — check the axilla, groin, and inguinal folds carefully), regional lymphadenopathy, Weil-Felix (OX-K) positive, IgM ELISA positive, responds to doxycycline. (5) Chikungunya — often coexists with dengue in urban outbreaks, severe polyarthralgia and arthritis (small joints of hands and feet, may persist for months), rash, IgM positive. (6) Typhoid — sustained stepwise fever, relative bradycardia, rose spots, hepatosplenomegaly, Widal or blood culture positive. (7) Sepsis with DIC — hypotension, organ dysfunction, positive blood culture. (8) Viral haemorrhagic fevers (Kyasanur Forest disease in Karnataka, CCHF in Rajasthan/Gujarat) — endemic areas, occupational exposure. NEET PG most commonly tests the dengue-versus-leptospirosis and dengue-versus-scrub-typhus distinctions.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
Written by: NEETPGAI Editorial Team
Reviewed by: Pending SME Review
Last reviewed: July 2026
