Dengue

Dengue is a viral infection transmitted to humans through the bite of infected Aedes mosquitoes, primarily Aedes aegypti. It is common in tropical and subtropical regions and is considered a major public health concern globally. Although not endemic to the UK, dengue can affect travellers returning from endemic areas. Dengue ranges in severity from mild illness to severe, life-threatening complications such as dengue haemorrhagic fever and dengue shock syndrome.

Causes

Dengue is caused by the dengue virus (DENV), which belongs to the Flaviviridae family. There are four closely related serotypes (DENV-1 to DENV-4). Infection with one serotype provides lifelong immunity to that type but not to others. A second infection with a different serotype increases the risk of severe disease due to antibody-dependent enhancement.

Pathophysiology

After a mosquito bite, the virus enters the bloodstream and infects white blood cells, leading to an immune response. The virus disrupts the vascular endothelium, causing increased capillary permeability, plasma leakage, and in some cases, coagulopathy. In severe cases, this leads to haemorrhage, fluid loss, shock, and multi-organ dysfunction. The incubation period is usually 4 to 10 days.

Signs and Symptoms

Symptoms typically begin suddenly and may include:

• High fever (up to 40°C)
• Severe headache, especially behind the eyes
• Muscle and joint pain (hence the nickname “breakbone fever”)
• Nausea, vomiting, and loss of appetite
• Skin rash (usually appears 3–4 days after fever onset)
• Mild bleeding (e.g. nosebleeds, gum bleeding, easy bruising)
• Fatigue and weakness

In severe dengue, symptoms may progress to abdominal pain, persistent vomiting, bleeding, and signs of shock (low blood pressure, cold extremities, rapid pulse).

Risk Factors

• Travel to or residence in endemic regions (e.g. South Asia, Southeast Asia, South America)
• Lack of prior exposure (more likely to experience severe disease upon second infection)
• Young children and the elderly
• Individuals with chronic conditions (e.g. diabetes, cardiovascular disease)
• Immunocompromised patients
• Pregnancy, which may increase risk of complications and vertical transmission

Investigations

Dengue is primarily diagnosed using laboratory tests:

• NS1 antigen test: Detects early viral antigen (usually within the first 5 days)
• RT-PCR: Confirms viral RNA, especially in early infection
• IgM and IgG serology: Detects antibodies, useful after day 5 of illness
• Full blood count: May show low white blood cells, low platelets, and rising haematocrit (suggesting plasma leakage)
• Liver function tests: May be mildly elevated
• Ultrasound: Can detect pleural effusion or ascites in severe dengue
• Routine imaging is not typically required unless complications are suspected.

Management

1. Non-Pharmacological Management

• Close monitoring of fluid balance, especially during the critical phase (days 3–7)
• Encourage oral rehydration with fluids like ORS, coconut water, or soup
• Bed rest and symptom monitoring
• Hospitalisation for severe dengue, especially if signs of bleeding, shock, or organ involvement appear

2. Pharmacological Management

• Paracetamol is the preferred antipyretic. Avoid NSAIDs like ibuprofen and aspirin due to bleeding risk
• Intravenous fluids (e.g. isotonic saline) for patients with signs of dehydration or shock
• Platelet transfusions are usually not required unless active bleeding occurs with severe thrombocytopenia
• No specific antiviral treatment for dengue currently exists

3. Surgical Management

There is no surgical treatment for dengue itself. However, surgery may be needed for complications like internal bleeding, although this is rare and typically managed conservatively.

Complications

• Dengue haemorrhagic fever (DHF): Plasma leakage, low platelet count, bleeding
• Dengue shock syndrome (DSS): Circulatory failure, hypotension, multi-organ dysfunction
• Severe bleeding: Gastrointestinal, intracranial, or mucosal
• Liver damage
• Neurological involvement: Encephalitis, seizures (rare)
• Complications in pregnancy: Preterm birth, low birth weight, vertical transmission

References

• NICE Clinical Knowledge Summary: Viral Infections in Returning Travellers
• Public Health England (now UKHSA): Guidance on dengue and returning travellers
• World Health Organization (WHO) Dengue Guidelines
• Royal College of Physicians: Managing Imported Infections
• NHS Fit for Travel: Dengue Information
• British Medical Journal (BMJ): Clinical Review on Dengue