Clinical Guides
Dengue Fever
An India-adapted clinical guide to recognising dengue across its febrile, critical and recovery phases, identifying plasma leakage and shock early, and using fluids and blood products safely.
MedNext Academy | 13 min read
Dengue Fever
An India-adapted clinical guide to recognising dengue across its febrile, critical and recovery phases, identifying plasma leakage and shock early, and using fluids and blood products safely.
Summary
Dengue is an acute mosquito-borne viral illness caused by one of four dengue virus serotypes. Its early fever, headache, retro-orbital pain, myalgia, nausea and rash overlap with many infections, so the decisive task is repeated clinical classification rather than a single diagnostic label. Most patients recover with oral fluids, paracetamol and observation. A minority enter a critical phase near defervescence, when increased vascular permeability can cause plasma leakage, haemoconcentration, pleural effusion, ascites and shock. Severe bleeding or organ involvement may also define severe dengue. Falling temperature is therefore not automatically reassuring.
The safe bedside model follows three phases: febrile, critical and recovery. During the febrile phase, establish hydration, risk factors, day of illness and a baseline full blood count. Around days three to seven, actively seek warning signs: severe abdominal pain, persistent vomiting, mucosal bleeding, clinical fluid accumulation, lethargy or restlessness, liver enlargement, and a rising haematocrit with rapidly falling platelets. Shock may first appear as narrow pulse pressure, cool extremities, delayed capillary refill or oliguria before frank hypotension. Management is supportive and response-led. Fluids must be sufficient to restore perfusion but reduced promptly as leakage resolves; indiscriminate boluses cause pulmonary oedema. Platelet count alone neither diagnoses shock nor justifies routine prophylactic transfusion. This is an reviewed educational guide educational draft assigned to the MedNext Clinical Team, not evidence of completed review.
How Common Is It?
Dengue occurs in tropical and subtropical regions and imposes a large, fluctuating global burden. Transmission varies by rainfall, temperature, mosquito density, urban water storage, population movement, circulating serotypes, immunity and surveillance intensity. WHO reports major recent expansion, but global notifications cannot be treated as an Indian prevalence rate: laboratory access, case definitions and reporting completeness differ between and within countries. Likewise, a tertiary hospital series over-represents warning signs and severe disease, while community infections may never be tested.
India experiences seasonal and geographically heterogeneous transmission. The practical history should include residence, travel during the preceding two weeks, similar illness locally and timing relative to monsoon or known outbreaks, but absence of a declared outbreak does not exclude dengue. Previous infection with one serotype does not provide durable protection against all others; secondary infection can be associated with greater risk of severe disease, although no bedside history can predict an individual course with certainty. Infants, pregnant people, older adults and patients with diabetes, hypertension, renal, hepatic or cardiac disease require a lower threshold for observation because physiological reserve and fluid tolerance differ.
Burden should be communicated without alarmism. Most symptomatic patients do not develop shock, and early recognition plus careful supportive treatment markedly improves safety. Conversely, reassuring prevalence statistics cannot override warning signs in an individual. Clinicians should consult current NCVBDC, state surveillance and local laboratory advice during an outbreak because testing algorithms and reporting arrangements may change.
Risk Factors
Exposure risk rises where competent Aedes mosquitoes, viraemic humans and conditions for daytime biting coexist. Uncovered water containers, construction sites, discarded tyres and intermittent water supply can create breeding habitats. Aedes mosquitoes often bite during daylight, so bed nets alone are incomplete protection; repellents, clothing, screens and removal of breeding sites remain relevant. Household clustering may occur, but dengue is not ordinarily spread by casual person-to-person contact. Rare routes such as transfusion, transplantation or vertical transmission do not change routine community counselling.
Risk of a complicated course is not reducible to platelet count. Prior dengue infection with a different serotype, infancy, pregnancy, older age and important comorbidity can increase concern. Diabetes, obesity, hypertension, chronic kidney disease, heart disease, chronic liver disease, haemoglobinopathy, anticoagulant use and limited ability to return for review affect triage. Social risk matters: long travel time, living alone, language barriers, inability to maintain oral intake or lack of a reliable caregiver may make outpatient monitoring unsafe even without a biological warning sign.
Iatrogenic risk is preventable. Aspirin and non-steroidal anti-inflammatory drugs can aggravate bleeding risk; intramuscular injections and unnecessary invasive procedures should be avoided. Excessive intravenous fluid, failure to reassess after a bolus, and continuing critical-phase rates into recovery can cause fluid overload. Prophylactic platelet transfusion exposes patients to transfusion reactions without reliably preventing bleeding. A risk factor should change surveillance or management, not be presented as destiny or used to deny care.
Diagnosis
History
Record the exact first day of fever and construct a daily timeline. Ask about headache, retro-orbital pain, myalgia, arthralgia, rash, nausea, vomiting, abdominal pain, diarrhoea, bleeding, reduced urine, breathlessness, postural dizziness and altered behaviour. Determine oral intake, pregnancy, comorbidity, medicines including aspirin, NSAIDs and anticoagulants, previous dengue, travel and local exposure. Ask specifically whether fever has just settled while abdominal pain, vomiting, bleeding, drowsiness or restlessness has appeared.
Examination
Assess airway, breathing, circulation, mental state and glucose before pursuing a label. Record temperature, pulse, respiratory rate, blood pressure and pulse pressure; inspect for mucosal bleeding, petechiae and rash. Examine capillary refill, extremity temperature, pulse volume, hydration, lungs, abdomen, liver size and evidence of ascites or pleural fluid. Repeat observations because a single normal blood pressure can coexist with compensated shock. Weigh the patient when fluid therapy may be needed.
Investigations
A full blood count provides haematocrit and platelet trends, but neither value should be interpreted alone. A rising haematocrit relative to baseline supports plasma leakage; a falling haematocrit in an unstable patient may reflect bleeding or dilution. NS1 antigen or nucleic-acid testing is most useful early, whereas IgM becomes useful later; follow the current local algorithm and illness day. A negative early or late test outside its optimal window does not automatically exclude dengue. Check glucose, electrolytes, renal and liver function, coagulation, lactate, blood gas, group and crossmatch, ECG or imaging when severity or organ involvement warrants them. Ultrasound can demonstrate fluid leakage but is not routine proof in every stable outpatient.
Differential Diagnosis
An acute undifferentiated fever in India requires a geography-, season- and exposure-based differential. Malaria must be tested for promptly where plausible because delay can be fatal and coexistence is possible. Chikungunya may produce prominent persistent joint pain; Zika is often milder but has major pregnancy implications. Leptospirosis, enteric fever, scrub typhus, rickettsial infection, influenza, COVID-19 and other viral illnesses may resemble early dengue. Local outbreaks should refine testing without creating tunnel vision.
Sepsis, meningococcaemia and other bacterial infections must be considered when shock, altered consciousness, focal infection or toxic appearance is present. Acute hepatitis, pancreatitis, appendicitis, cholecystitis and other surgical abdominal disease may cause pain and abnormal liver tests. Thrombotic thrombocytopenic purpura, immune thrombocytopenia, acute leukaemia, aplastic processes and drug-related cytopenias can produce low platelets but do not share the same illness trajectory. Pregnancy-related conditions such as pre-eclampsia, HELLP syndrome and obstetric haemorrhage require simultaneous obstetric assessment.
The pattern of haematocrit and physiology helps but is not infallible. Rising haematocrit with falling platelets near defervescence supports plasma leakage; low or falling haematocrit with instability may indicate bleeding, haemodilution or a low baseline. A positive dengue test does not exclude bacterial sepsis, malaria or a surgical emergency. Similarly, a rash and thrombocytopenia do not prove dengue. Revisit the differential whenever the course is atypical, fever persists beyond the expected phase, focal signs emerge or the patient fails to respond to appropriate supportive care.
Management
Classify the patient after each assessment as dengue without warning signs, dengue with warning signs or severe dengue, while also considering comorbidity and social safety. A stable patient who drinks adequately, passes urine, has no warning sign and can return reliably may be managed as an outpatient with oral fluids, rest, paracetamol within locally approved limits, mosquito-bite prevention and explicit daily review around the critical period. Provide written instructions that defervescence can precede deterioration. Avoid aspirin, ibuprofen and other NSAIDs.
Warning signs, significant risk factors or poor oral intake usually require facility observation or admission under the current NCVBDC and local pathway. Obtain a baseline haematocrit when possible without delaying needed treatment. Use isotonic crystalloid only for a defined indication, calculate by actual clinical context and ideal body weight where the protocol specifies, and reassess pulse pressure, perfusion, capillary refill, respiratory status, urine output and haematocrit after each intervention. The correct rate changes with response; this guide deliberately does not function as a fluid chart.
Shock needs senior-led emergency resuscitation and frequent reassessment. A persistently high or rising haematocrit suggests continuing leakage and possible need for further protocolised fluid, whereas falling haematocrit with instability raises concern for major bleeding and blood replacement. Once perfusion improves, taper fluid; during recovery, mobilised extravascular fluid increases overload risk. Monitor for respiratory distress, basal crackles, rising jugular venous pressure, enlarging effusions and declining oxygenation. There is no routine antiviral therapy. Treat documented organ complications and coinfections without attributing every abnormality to dengue.
Prescribing Information
Paracetamol may be used for fever and pain in dengue when clinically appropriate, but the prescriber must account for age, weight, liver function, alcohol use, combination products and doses already taken. This guide does not provide a personal dose. Aspirin and non-steroidal anti-inflammatory drugs should be avoided because platelet dysfunction and gastrointestinal injury can compound bleeding. Intramuscular injections and unnecessary anticoagulants or antiplatelets should be reviewed with senior input; patients on essential long-term therapy need an individual risk-benefit decision, not abrupt unsupervised discontinuation.
Intravenous crystalloid is a treatment with dose, indication and toxicity. Prescribe the solution, rate, duration, reassessment time and stopping criteria. Use repeated clinical and haematocrit response rather than a fixed daily volume. Children, pregnant patients, older adults and those with renal or cardiac disease are especially vulnerable to both under-resuscitation and overload. Colloids, vasopressors and organ support belong to experienced teams treating refractory shock after reassessing leakage, bleeding, sepsis and myocardial dysfunction. Diuretics are not a remedy for uncorrected dengue shock; their use during recovery requires careful haemodynamic assessment.
Do not transfuse platelets solely because the count is low. NCVBDC notes that prophylactic transfusion is generally not recommended; active clinically important bleeding, exceptional very low counts, urgent procedures and coagulation abnormalities require protocol-based specialist judgement. Major occult bleeding with shock and a falling haematocrit may require crossmatched packed red cells or whole blood. Fresh frozen plasma is not a routine correction for laboratory values without bleeding. Every blood product carries volume, allergic, infectious and alloimmunisation risks, so document the clinical indication and response.
When to Refer
Arrange urgent hospital assessment for any warning sign: severe or persistent abdominal pain, repeated vomiting, mucosal bleeding, lethargy, restlessness, clinical fluid accumulation, liver enlargement or a rising haematocrit with a rapid platelet fall. Refer patients who cannot drink, pass little urine, are becoming breathless, have postural symptoms, live too far to return safely or have important pregnancy, age or comorbidity risk. A falling fever should never delay referral when the patient is clinically worse.
Emergency transfer to a facility capable of monitored resuscitation is required for shock, severe bleeding, respiratory distress, altered consciousness, seizure, myocarditis, severe hepatitis, acute kidney injury or other organ dysfunction. Stabilise airway, breathing and circulation; obtain appropriate vascular access; monitor during transport; and speak directly to the receiving team. The handover should state illness day, temperature trajectory, warning signs, serial pulse pressure, perfusion, urine output, weight, haematocrit and platelet trends, tests, fluids with exact timing, bleeding, comorbidity and pregnancy status.
Escalate within hospital when the patient fails to improve after an initial protocolised intervention. Reassess the diagnosis, ongoing leakage, concealed bleeding, sepsis, cardiogenic impairment and iatrogenic overload rather than repeating fluid automatically. Obstetric, paediatric, critical-care, haematology or organ-specific advice may be needed. Discharge from observation requires improving clinical status, stable haemodynamics without intravenous support, adequate oral intake and urine output, resolving warning signs and a safe follow-up plan under local criteria.
Red Flags
The most dangerous transition often occurs near defervescence. Severe abdominal pain, persistent vomiting, haematemesis, melaena, heavy vaginal bleeding, new confusion, profound lethargy, restlessness, cold clammy skin, weak rapid pulse, delayed capillary refill, narrowing pulse pressure, hypotension, oliguria and breathlessness require immediate reassessment. Do not wait for a critically low platelet count or a positive confirmatory test. Compensated shock can exist while systolic pressure remains apparently normal.
Severe dengue includes severe plasma leakage leading to shock or respiratory distress, severe bleeding, or major organ involvement. Concerning organ features include encephalopathy, seizures, marked transaminase elevation with hepatic dysfunction, myocarditis or arrhythmia, acute kidney injury and severe metabolic disturbance. Pregnancy adds fetal and maternal concerns; children may deteriorate with fewer verbal complaints. An infant who becomes unusually drowsy, refuses feeds or develops cool mottled limbs needs urgent care.
Treatment itself can create red flags. Increasing respiratory rate, oxygen requirement, crackles, tense ascites, raised jugular venous pressure, gallop rhythm or sudden hypertension during recovery may indicate fluid overload. Worsening shock with a falling haematocrit suggests significant bleeding; worsening shock with a high or rising haematocrit suggests ongoing leakage, although context matters. Transfusion reactions require stopping the product and activating the local protocol. A patient sent home must be told to return immediately for any warning sign, reduced urine or inability to drink, and must not rely on a home platelet count as the sole safety measure.
Indian Clinical Context
NCVBDC's 2023 national guideline is the principal India-specific clinical source used here. It classifies mild, moderate and severe dengue, emphasises illness phase, warning signs, serial haematocrit, judicious fluid therapy and restricted blood-product use. State circulars, facility protocols and laboratory capacity may add operational detail, so clinicians should verify the current local pathway rather than copy a static online schedule. Suspected and confirmed cases should be notified through the legally and administratively applicable state or national surveillance mechanism; requirements can change and the treating facility's infection-control or surveillance officer should confirm the route.
Access constraints can alter safe disposition. Patients may travel several hours, pay for repeated counts or lack a caregiver who recognises deterioration. These factors should lower the threshold for observation when the critical phase is approaching. Counselling should use the patient's preferred language and explain that platelet count is only one part of monitoring. Commercial pressure for serial tests or prophylactic platelets should be resisted when it does not improve care. Equally, limited resources must not justify delaying transfer of shock.
Prevention belongs in clinical management because a viraemic patient can infect mosquitoes. Advise repellents, covered clothing, screens and bed nets during illness, including daytime rest, and elimination of water-holding containers around the home. Community vector control is not achieved by indiscriminate household fogging alone. Public messages should avoid unproven papaya-leaf or other remedies as substitutes for hydration and review. This draft remains quarantined for organisational clinical review and does not replace NCVBDC, state public-health or hospital protocols.
NMC Competency Mapping
Dengue supports integrated NMC CBME learning across medicine, paediatrics, community medicine, microbiology, pathology, pharmacology, obstetrics and emergency care. At Know level, learners should describe Aedes transmission, dengue serotypes, febrile-critical-recovery phases, warning signs and the definitions of severe plasma leakage, severe bleeding and organ involvement. They should explain why a rapid platelet fall is a risk signal but not a transfusion order, and why haematocrit must be interpreted against baseline, fluids and bleeding.
At Know How level, learners should construct an illness-day timeline, classify severity, choose phase-appropriate testing and distinguish leakage from haemorrhage. They should compare malaria, chikungunya, leptospirosis, scrub typhus, enteric fever, sepsis and surgical abdominal disease using clinical and epidemiological clues. At Show How level, a simulation should require recognition of compensated shock, calculation only after weight and local protocol are available, response-led reassessment, and a concise referral handover.
At Perform level, supervised practice includes recording pulse pressure and perfusion accurately, charting intake and urine output, reviewing serial haematocrit, counselling on warning signs and participating in surveillance notification. Learners must not independently prescribe fluid boluses, blood products or discharge based on this guide. Professional competencies include avoiding unnecessary transfusion, explaining uncertainty, obtaining consent, communicating across language barriers and reporting public-health data without breaching confidentiality. Mapping is educational; it does not claim completion of any NMC competency from reading one page.
Key Exam Pearls for NEET PG
Dengue classically progresses through febrile, critical and recovery phases. The critical phase commonly begins around defervescence, so a patient who is afebrile but newly vomiting, drowsy or poorly perfused may be deteriorating. Warning signs include abdominal pain or tenderness, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy or restlessness, hepatomegaly and increasing haematocrit with rapidly falling platelets. Severe dengue means severe plasma leakage causing shock or respiratory distress, severe bleeding, or severe organ involvement.
NS1 antigen and nucleic-acid methods are most useful early; IgM becomes more useful later. Test timing matters. Leukopenia and thrombocytopenia may occur, but serial haematocrit is the more direct clue to plasma leakage. A rising haematocrit in shock suggests leakage; a falling haematocrit with ongoing instability suggests bleeding or dilution. Pulse pressure can narrow before hypotension. Urine output and capillary refill are essential response markers.
Treatment is supportive. Encourage oral isotonic fluids when safe, use paracetamol rather than aspirin or NSAIDs, and give carefully titrated isotonic crystalloid for warning signs or shock according to the current protocol. Reduce fluids as physiology improves and leakage ends. Platelet count alone is not an indication for prophylactic transfusion; clinically important bleeding and haemodynamic context drive blood-product decisions. Aedes bites mainly by day, although protection should be continuous. Prior infection does not prevent infection by another serotype and may be associated with greater severe-disease risk.
Frequently Asked Questions
Can dengue become more dangerous after the fever has gone down?
Yes. The critical phase often begins near defervescence, when plasma leakage may develop. New abdominal pain, repeated vomiting, bleeding, drowsiness, restlessness, reduced urine, cold extremities or breathlessness after the temperature falls needs urgent reassessment rather than reassurance. A normal temperature must therefore be interpreted alongside circulation, urine output, examination and illness day.
Does a very low platelet count always require platelet transfusion?
No. Platelet count alone does not measure perfusion or prove active bleeding, and routine prophylactic transfusion has not shown reliable benefit. The treating team considers clinical bleeding, haemodynamics, coagulation, procedures and exceptional very low counts under the current protocol. Unnecessary transfusion can cause reactions and fluid overload without correcting plasma leakage.
How should haematocrit be interpreted during dengue treatment?
Trend it against the patient's baseline and clinical state. Rising haematocrit with poor perfusion can suggest continuing plasma leakage; falling haematocrit with instability may suggest bleeding or dilution. Fluids themselves alter the value, so timing and repeated examination matter. A single result should never replace pulse pressure, capillary refill, respiratory assessment and urine-output monitoring.
What should a patient managed at home be told before leaving?
They need clear oral-fluid and paracetamol advice, avoidance of aspirin and NSAIDs, mosquito-bite prevention, a planned review around the critical period, and immediate return for warning signs, reduced urine, inability to drink or any clinical deterioration. Instructions should be written in a language the patient or caregiver understands and include a feasible return destination.
Inside MedNext for this topic
- 411 MedNext-authored chapters
- 80,000+ MCQ bank
- 15 study modes
- a growing library of visual revision sheets
Study modes
- Notes
- MCQ
- Audio
- Video
- Visual
- 3D Anatomy
- Trace
- Flashcards
- Mnemonics
- Image Bank
- Clinical
- Microscopy
- Audio QBank
- Cadaver
- Book Match
Continue reading
Clinical GuidesAll Clinical Guides
Browse all clinical management guides for Indian medical practice.
Test your knowledge
Attempt structured MCQs on this topic to consolidate your understanding and connect the guide to exam-focused practice.
Try MCQs on this topic