Dengue fever
Know the day of illness, watch for warning signs as the fever settles, give fluids by protocol only when needed, and do not chase the platelet count.
A 26-year-old man from Rawalpindi had fever for four days. The fever settled this morning and his family is relieved, but he has belly pain and has vomited three times. Pulse 112, BP 108/94, cold hands. Platelets 38,000/µL, haematocrit 49% (yesterday 41%).
Is he getting better or worse, and what do you do?
- Ask the day of illnessWrite it on the file and in every note: "Day 4 of fever, afebrile since morning".
- Check perfusion, not just temperaturePulse, BP, pulse pressure, capillary refill, cold hands, urine output.
- Look for warning signsAt every review. Any one means admit and start the warning-sign pathway.
- CBC with haematocrit and plateletsToday and daily. Haematocrit before starting any IV fluid.
- DiagnosisNS1 antigen if fever under 5 days. Dengue IgM from day 5.
- Fluids by groupOral if no warning signs. IV by protocol for warning signs or shock.
- Paracetamol onlyNo NSAIDs, aspirin or intramuscular injections.
- Single monitoring chartDay of illness, haematocrit, platelets, vitals, fluid rate and urine side by side.
- Any warning sign
- Cold hands, slow capillary refill, pulse pressure 20 mmHg or less, low BP
- Bleeding: vomiting blood, black stools, heavy periods, gum bleeding that will not stop
- Haematocrit rising while platelets fall fast
- Drowsy, confused, very little urine
- Pregnant, infant, elderly, or heart or kidney disease
| Critical phase | Usually day 3–7, as the fever settles. Lasts 24–48 hours |
| Warning signs | Crystalloid 5–7 mL/kg/hour for 1–2 hours, then step down |
| Shock | Crystalloid 10–20 mL/kg, then reassess and recheck haematocrit |
| Urine target | About 0.5 mL/kg/hour. Much more means too much fluid |
| Platelets | Do not transfuse for a low count alone. Only for significant bleeding |
| Fever | Paracetamol 1 g every 6 hours, maximum 4 g a day |
Check every dose against a current drug reference and your hospital protocol.
On this page
What dengue is
Dengue is a viral infection spread by Aedes mosquitoes, which bite in the daytime. In Pakistan it comes in waves after the monsoon, roughly August to November, with large outbreaks in Lahore, Rawalpindi, Karachi and Peshawar.
Most patients have a short, unpleasant fever and recover on their own. A smaller number develop plasma leakage: the small blood vessels become leaky, fluid escapes into the tissues, the belly and the chest, the blood becomes concentrated (the haematocrit rises), and the patient can go into shock.
The danger comes as the fever settles, not at its peak. Families relax when the fever breaks. That is exactly when patients crash. Write the day of illness on every note: it tells you more about risk than the platelet count does.
The three phases
- Day 1–3Febrile phase: high fever, aches
- Day 3–7Critical phase: fever settles, plasma leaks
- 24–48 h laterRecovery: leaked fluid returns
| Phase | What happens | What you do |
|---|---|---|
| Febrile | High fever, severe body and joint pain, headache, pain behind the eyes, flushed face, rash. NS1 positive. | Paracetamol, oral fluids, daily CBC, teach the warning signs |
| Critical | Plasma leak for 24–48 hours: haematocrit rises, platelets fall, fluid in the belly and chest, risk of shock and bleeding | Close monitoring. IV fluids by protocol only if warning signs or shock |
| Recovery | Fluid returns to the blood vessels. Appetite returns, itchy rash with "islands of white in a sea of red", slow pulse, lots of urine | Stop IV fluids. Watch for fluid overload |
Warning signs
- Belly pain or tenderness.
- Vomiting that keeps happening.
- Fluid in the belly or chest (ascites, pleural effusion).
- Bleeding from gums, nose or other mucosa.
- Lethargy or restlessness.
- Liver enlarged more than 2 cm.
- Laboratory: haematocrit rising at the same time as platelets falling fast.
- Fast pulse, cold hands and feet, capillary refill over 2 seconds.
- Narrow pulse pressure: 20 mmHg or less (for example 108/94).
- Restless, very little urine.
- Low BP is a late sign. Young patients keep a normal systolic BP until they are close to collapse.
Who goes where
- Drinking well
- Passing urine at least every 6 hours
- No warning signs
- No high-risk features
- Any warning sign
- Or high-risk: pregnancy, infant, elderly, diabetes, heart or kidney disease
- Or cannot drink, lives far away, alone
- Dengue shock
- Severe bleeding
- Organ failure (liver, brain, heart)
History and examination
- Day of illness: count from the first day of fever.
- Vomiting, belly pain, bleeding, how much they are drinking, when they last passed urine.
- Pregnancy, diabetes, heart or kidney disease, other medicines (especially NSAIDs taken for the fever).
- Examine: pulse, BP and pulse pressure, capillary refill, temperature of the hands, liver size, fluid in the belly or chest, bleeding spots, and mental state.
- Tourniquet test is of limited use. Do not let it delay the assessment.
Investigations
| Test | Why | What to look for |
|---|---|---|
| CBC with haematocrit | Leak and bleeding | Rising haematocrit = leak. Falling haematocrit in a shocked patient = bleeding |
| Platelets | Severity trend | Rapid fall alongside rising haematocrit is a warning sign |
| NS1 antigen | Diagnosis in the first 5 days | Positive confirms dengue. Negative does not exclude it |
| Dengue IgM | Diagnosis from day 5 | Positive supports recent dengue |
| LFTs | Liver involvement | ALT and AST often raised. Very high values mean severe disease |
| Urea, creatinine, electrolytes, sugar, calcium | Organ function in group B and C | Kidney injury, low sugar, low calcium |
| Ultrasound | Leak | Fluid in the belly or chest, thickened gallbladder wall |
| Malaria test, blood culture | Other causes of fever | Co-infection is possible |
Group A: treating at home
- Rest. Plenty of oral fluids: ORS, juice, soup, lassi, coconut water, not just plain water. About 2.5 litres a day for an adult.
- Paracetamol for fever and pain. Tepid sponging is fine.
- No NSAIDs (ibuprofen, diclofenac), no aspirin, no intramuscular injections. They increase bleeding.
- Daily review with CBC until 48 hours after the fever has settled.
- Written advice on warning signs and when to come back immediately.
Group B: warning signs
- Haematocrit before startingThis is your baseline for every decision that follows.
- Crystalloid 5–7 mL/kg/hour for 1–2 hours0.9% sodium chloride or Ringer's lactate.
- Then 3–5 mL/kg/hour for 2–4 hoursIf the pulse, BP, capillary refill and urine are improving.
- Then 2–3 mL/kg/hourContinue reassessing.
- Reassess after every stepPulse, BP, pulse pressure, capillary refill, urine output, haematocrit.
- Worse, or haematocrit risingGo back up a step.
- Aim for urine about 0.5 mL/kg/hourMore than this usually means too much fluid.
- Stop after 24–48 hoursAs the leak ends and the patient drinks well.
Group C: dengue shock
- Crystalloid 5–10 mL/kg/hour over 1 hour
- Reassess
- Improving: step down to 7–10, then 5–7, 3–5, 2–3 mL/kg/hour over 24–48 hours
- Crystalloid 20 mL/kg over 15–30 minutes
- Reassess
- Improving: step down as for compensated shock
- Ongoing leak
- Second crystalloid bolus
- By the third bolus, discuss colloid with your senior
- Hidden bleeding, often from the gut
- Transfuse: fresh whole blood 10–20 mL/kg or packed red cells 5–10 mL/kg
- Senior now
- Call your senior. Oxygen. Two cannulas. Group and cross-match.
- Correct low sugar, low calcium and acidosis.
- Urinary catheter with hourly urine output.
- HDU or ICU for patients in shock.
Patients in dengue shock often keep a normal systolic BP until late. A narrow pulse pressure, cold hands and a fast pulse mean shock even when the BP looks fine.
Platelets and bleeding
- A low platelet count by itself is not an emergency and does not need a transfusion.
- Giving platelets "to be safe" does not prevent bleeding or death in dengue, and can cause fluid overload. WHO advises against it.
- The count usually rises by itself within a few days, in the recovery phase.
- What saves lives is close monitoring and the right amount of fluid at the right time.
- Papaya leaf juice and "drips" are not treatments. Explain kindly and firmly.
- Transfuse platelets (and blood if needed) only for significant active bleeding, after discussion with your senior.
- Avoid intramuscular injections, NG tubes and arterial punctures where possible.
- Steroids are not recommended in dengue.
Recovery phase
- Signs: feels better, appetite returns, stable pulse and BP, good urine output, haematocrit falling, platelets rising, sometimes a slow pulse and an itchy rash.
- Stop IV fluids. Continuing them now causes pulmonary oedema and large pleural effusions.
- If the patient becomes breathless with crackles or a big effusion in this phase, it is fluid overload: stop fluids and discuss furosemide with your senior if the BP is stable.
Special groups
- Pregnancy: admit with any warning sign. Leak and bleeding are harder to judge. Involve obstetrics early. Delivery during the critical phase carries a high bleeding risk.
- Infants and young children: shock develops faster. Weight-based fluids and frequent sugar checks.
- Elderly, heart or kidney disease: smaller fluid steps and more frequent reassessment.
Monitoring on the ward
| Patient | What to monitor | How often |
|---|---|---|
| Warning signs | Pulse, BP, pulse pressure, capillary refill, urine output | Every 1–4 hours |
| Warning signs | Haematocrit | Before fluids, then every 6–12 hours |
| Shock | Vital signs and urine output | Every 15–30 minutes until stable, then hourly |
| Shock | Haematocrit | Before and after each bolus, then every 4–6 hours |
Going home
- No fever for 24–48 hours without paracetamol.
- Eating and drinking well, good urine output.
- Stable haematocrit and platelets rising (usually above 50,000/µL).
- No breathing difficulty from effusions.
Common mistakes
- Discharging a patient on the day the fever settles because "the fever is gone".
- Treating the platelet count instead of the patient.
- Calling a BP of 108/94 "normal". The pulse pressure is 14: that is shock.
- Running fluids at the same high rate for days, into the recovery phase.
- Giving ibuprofen, diclofenac or IM injections for the fever.
- Forgetting that a falling haematocrit in a shocked patient means bleeding.
Frequently asked questions
What are the warning signs in dengue?
Belly pain or tenderness, persistent vomiting, fluid in the belly or chest, mucosal bleeding, lethargy or restlessness, a liver enlarged more than 2 cm, and a rising haematocrit with a rapid fall in platelets.
When is platelet transfusion needed in dengue?
Only for significant active bleeding, after senior review. A low platelet count without bleeding is not an indication for transfusion.
What IV fluid rate is used for dengue with warning signs?
Crystalloid at 5–7 mL/kg/hour for 1–2 hours, then 3–5 mL/kg/hour for 2–4 hours, then 2–3 mL/kg/hour, reassessing and checking the haematocrit at each step.
When is the critical phase of dengue?
Usually around days 3 to 7 of illness, as the fever comes down. It lasts about 24 to 48 hours.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 24-year-old man with dengue is on day 5. His fever has gone. BP 106/92, pulse 118, cold hands. What is the best description?
Answer: Compensated dengue shock. Narrow pulse pressure (20 mmHg or less), fast pulse and cold peripheries as the fever settles indicate compensated shock from plasma leakage. Group C: IV fluids per protocol and senior review.
- Fluid overload: Cold peripheries and narrow pulse pressure suggest low volume.
- Recovery phase: Defervescence is when the critical phase starts.
- Normal BP, so stable: Pulse pressure 14 mmHg with tachycardia and cold peripheries is shock.
- Dengue fever without warning signs: He has signs of shock.
2. A dengue patient has platelets 18,000/µL. She has no bleeding and stable observations. What is the best management?
Answer: Monitor closely; no platelet transfusion. Platelet transfusion is reserved for significant bleeding. Low platelets alone are not an indication.
- Discharge as platelets are stable: She needs monitoring in the critical phase.
- Give fresh frozen plasma: Not indicated without bleeding.
- Start IV steroids: No benefit.
- Transfuse platelets now: Prophylactic platelets do not prevent bleeding or shock in dengue.
3. A dengue patient in shock has had two fluid boluses but is not improving. The haematocrit has fallen from 52% to 38%. What is the most likely explanation?
Answer: Hidden bleeding: transfuse blood. In dengue shock, a falling haematocrit without improvement suggests internal bleeding, often from the gut. Give blood and call the senior.
- Successful fluid resuscitation: A falling haematocrit with ongoing shock means blood loss.
- Recovery phase: Shock is persisting.
- Lab error: Act on it.
- Haemodilution only; give more crystalloid: Ignores the likely bleed.
4. On day 5 of a febrile illness in Lahore during the post-monsoon season, a 25-year-old woman’s fever settles. She now has abdominal pain, persistent vomiting and a rising haematocrit with platelets 40 × 10⁹/L. What is this phase?
Answer: Critical (plasma leakage) phase. Dengue has three phases: febrile (2–7 days), critical (around defervescence, 24–48 h of plasma leakage), and recovery. WHO warning signs: abdominal pain, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy/restlessness, liver > 2 cm, and rising haematocrit with falling platelets. These patients need admission and careful isotonic crystalloid guided by haematocrit and urine output. Avoid NSAIDs and IM injections; prophylactic platelet transfusion is not recommended.
- Recovery phase: In recovery the haematocrit falls.
- Febrile phase: The fever has settled, so the febrile phase has passed.
- Dengue fever without warning signs: She has warning signs: abdominal pain, vomiting and rising haematocrit.
5. A 22-year-old has had fever, retro-orbital headache and myalgia for 2 days in Rawalpindi. Which test best confirms dengue at this stage?
Answer: NS1 antigen. NS1 antigen and RT-PCR are positive in the first 5 days of fever; IgM becomes detectable from about day 5; IgG rises later (early high IgG suggests secondary infection, which carries greater risk of severe dengue). Leucopenia and thrombocytopenia support the diagnosis. Paracetamol for fever; avoid aspirin/NSAIDs.
- Dengue IgG: IgG indicates past or secondary infection.
- Tourniquet test: The tourniquet test is non-specific.
- Widal test: The Widal test is for typhoid.
6. A haematocrit of 41% means:
Answer: 41% of blood is red cells. Haematocrit (packed cell volume) is the fraction of blood volume made up of red cells after centrifugation; normal about 40–50% in men and 36–46% in women. Plasma forms the rest (with a thin buffy coat of white cells and platelets). It falls after haemorrhage only once fluid shifts dilute the blood (hours), and rises in dehydration and polycythaemia.
- 41% of blood is plasma: Plasma would be about 59%.
- 41% of red cells are reticulocytes: Reticulocytes are about 1%.
- Haemoglobin is 41 g/L: Different measure.
- 41% of white cells are neutrophils: Differential count.
7. During the monsoon, a young man in Lahore has high fever, severe body aches and retro-orbital pain. On day 5 his platelets fall to 40 × 10⁹/L and haematocrit rises by 20%. What is the diagnosis and key danger sign?
Answer: Dengue with plasma leakage. Dengue (flavivirus, Aedes aegypti, day-biting) causes fever, headache, retro-orbital pain, myalgia ('breakbone fever') and rash. The critical phase starts as fever settles (days 3–7): capillary leak causes rising haematocrit, falling platelets, effusions and shock. Management is careful fluid therapy; avoid NSAIDs and aspirin. NS1 antigen detects early infection. Secondary infection with another serotype raises the risk of severe dengue.
- Malaria with hypoglycaemia: No haematocrit rise pattern.
- Typhoid with perforation: Gradual fever, bradycardia.
- Chikungunya with arthritis: Severe joint pain, less leak.
- Crimean–Congo haemorrhagic fever: Tick-borne, severe bleeding, contact transmission.
References and dose sources
- WHO fact sheet: Dengue and severe dengue
- CDC: Dengue clinical presentation
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Oral rehydration salts (ORS) dosing: MSF Essential Drugs: Oral rehydration salts (see also our oral rehydration salts (ors) dose page)
- Ringer's lactate (Hartmann's solution) dosing: Drugs.com: Lactated Ringer's dosage (see also our ringer's lactate (hartmann's solution) dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.