Key Facts

Dengue is the most common arboviral infection worldwide, with increasing incidence due to urbanisation and climate change. Most UK cases are imported from endemic areas. Management is supportive, with careful attention to the critical phase around day 3–7.

Epidemiology

• Global: ~100–400 million infections/year; ~500,000 severe dengue cases; ~25,000 deaths (WHO)
• Endemic in >100 countries (tropical/subtropical)
• UK: ~300–500 imported cases/year; no autochthonous transmission (yet)
• Peak incidence in travellers returning from Southeast Asia (Thailand, India) and Caribbean
• Most common in adults aged 20–40

Aetiology

• Dengue virus: family Flaviviridae, 4 serotypes
• Transmitted by Aedes mosquitoes (bite during daytime)
• Incubation period: 4–10 days
• Risk of severe dengue: secondary infection with different serotype (antibody-dependent enhancement)

Pathophysiology

• Dengue virus infects monocytes, macrophages, dendritic cells
• Immune activation → cytokine storm → increased vascular permeability
• Antibody-dependent enhancement (ADE): pre-existing non-neutralising antibodies from prior infection with different serotype enhance viral uptake → higher viraemia → more severe disease
• Plasma leakage: occurs around defervescence (days 3–7) → haemoconcentration, pleural effusions, ascites
• Thrombocytopenia: peripheral destruction and bone marrow suppression
• Severe dengue: dengue haemorrhagic fever (DHF) or dengue shock syndrome (DSS)

Febrile Phase (Days 1–3)

• Sudden high fever (40°C)
• Severe headache, retro-orbital pain
• Myalgia, arthralgia (breakbone fever)
• Nausea, vomiting
• Maculopapular rash (may appear later)
• Facial flushing

Critical Phase (Days 3–7 — around defervescence)

• Temperature drops but clinical deterioration
• Plasma leakage: haemoconcentration (rising haematocrit), pleural effusion, ascites
• Haemorrhage: petechiae, epistaxis, gingival bleeding, menorrhagia, GI bleeding
• Dengue shock syndrome: tachycardia, narrow pulse pressure, hypotension, poor perfusion

Recovery Phase (Days 7–10)

• Gradual improvement
• Fluid reabsorption (risk of fluid overload if over-resuscitated)
• Convalescent rash (islands of white in sea of red)
• Pruritus

Red Flags (WHO warning signs for severe dengue)

• Abdominal pain or tenderness
• Persistent vomiting
• Clinical fluid accumulation (pleural effusion, ascites)
• Mucosal bleeding
• Lethargy/restlessness
• Hepatomegaly >2cm
• Laboratory: increasing haematocrit with rapidly decreasing platelets

Bedside

• Observations: temperature, BP (narrow pulse pressure in shock), HR
• Tourniquet test: inflate BP cuff between systolic and diastolic for 5 min — ≥20 petechiae per square inch = positive
• Blood glucose: hypoglycaemia in severe disease

Bloods

• NS1 antigen: positive days 1–5 (highly sensitive early)
• Dengue IgM/IgG: positive from day 5; IgG positive in secondary infection from day 1
• Dengue PCR: if available, confirms and serotypes
• FBC: leucopenia, thrombocytopenia (can be very severe <20 × 10⁹/L), haematocrit (rising = haemoconcentration)
• LFTs: transaminitis (AST > ALT typically)
• U&Es: AKI in severe cases
• Coagulation: prolonged in severe dengue/DIC
• CRP: usually low (helps distinguish from bacterial infection)

Imaging

• CXR: pleural effusions
• USS abdomen: ascites, gallbladder wall thickening (oedema), pleural effusions

Special Tests

• Serial haematocrit: rising haematocrit = plasma leakage (critical phase)
• Serial platelet count: guide bleeding risk
• Blood group and cross-match: if bleeding risk

Non-pharmacological

• Supportive care is the mainstay — no specific antiviral exists
• Oral fluid replacement: encourage oral rehydration in uncomplicated dengue
• Bed rest: during febrile and critical phases
• Close monitoring: daily FBC (haematocrit, platelets) during critical phase
• Avoid NSAIDs and aspirin: increased bleeding risk — use paracetamol only

Pharmacological

Uncomplicated dengue:

• Paracetamol 1g QDS for fever and pain (avoid NSAIDs)
• Oral rehydration solution
• Monitor for warning signs

Dengue with warning signs:

• IV crystalloid: 0.9% NaCl or Hartmann's — 5–7 ml/kg/hr for 1–2 hours, then reduce based on response
• Serial haematocrit and clinical assessment to guide fluid rate
• Avoid excessive fluids (risk of pulmonary oedema in recovery phase)

Severe dengue/dengue shock:

• Rapid IV crystalloid: 20 ml/kg bolus over 15–30 min
• If no improvement: consider colloid (e.g. gelatin solutions) or blood products
• Platelet transfusion: only if active bleeding with platelets <10 × 10⁹/L (prophylactic platelet transfusion not recommended)
• Packed red cells: if significant haemorrhage
• ICU admission: for shock, organ failure

Surgical/Interventional

• Rarely needed
• Pleural/peritoneal drainage: only if compromising respiration

Referral Criteria

• Infectious diseases/tropical medicine: all confirmed cases
• ICU: severe dengue, shock, organ failure
• Haematology: severe thrombocytopenia with bleeding
• Notify public health (notifiable disease in the UK)

• Overall dengue case-fatality rate: <1% with access to care
• Severe dengue without treatment: mortality up to 20%
• Severe dengue with expert management: mortality <1–5%
• Full recovery expected in uncomplicated dengue within 1–2 weeks
• Post-dengue fatigue: may persist for weeks to months
• Secondary infection with different serotype: higher risk of severe disease (ADE)
• UK imported dengue: no deaths in most years; rare fatalities with delayed recognition

WHO Dengue Classification (2009)

Dengue Timeline