Dengue Fever

What is dengue fever?

Dengue fever is a mosquito-borne viral infection caused by the dengue virus (DENV), transmitted by Aedes aegypti and Aedes albopictus mosquitoes. An estimated 390 million infections occur worldwide each year, of which around 96 million produce clinical illness, primarily in tropical and subtropical regions. Most cases cause a self-limiting febrile illness lasting 5–7 days. A small proportion progress to severe dengue (dengue haemorrhagic fever or dengue shock syndrome), which can be life-threatening without prompt hospital care.

Symptoms of dengue fever

Symptoms typically appear 4–10 days after a mosquito bite and include:

• Sudden high fever (39–40°C / 102–104°F)
• Severe headache, especially behind the eyes
• Intense muscle and joint pain ("breakbone fever")
• Skin rash: appears 2–5 days after fever starts
• Nausea and vomiting
• Fatigue and general weakness
• Mild bleeding: nose bleeds, gum bleeding, easy bruising

Dengue blood tests explained

Platelet count in dengue

What to do if you have dengue

• Rest: Complete bed rest is essential during the febrile phase
• Hydration: Drink at least 2–3 litres of fluids daily, oral rehydration salts (ORS), coconut water, clear broth, fruit juices
• Paracetamol only: Take paracetamol (acetaminophen) for fever and pain, do NOT take ibuprofen, aspirin or diclofenac (they increase bleeding risk)
• Monitor platelet count: Daily CBC from day 3 of fever
• Watch for warning signs: Go to hospital immediately if any danger signs appear
• Mosquito control: Use mosquito nets and repellent to prevent spreading dengue to others

There is no specific antiviral treatment for dengue

Treatment is supportive: managing fever, maintaining hydration and monitoring for complications. Dengue vaccines exist (Dengvaxia) but are only approved for people with previous dengue infection. Research into better vaccines continues. Prevention through mosquito control remains the most important public health tool.

Questions to ask your doctor

• Should I be admitted to hospital with this platelet count?
• How often should I recheck my CBC?
• When is it safe to return to work or school?
• Can I give dengue to family members at home?

References

The clinical information on this page is based on peer-reviewed sources indexed in PubMed, the biomedical literature database of the US National Library of Medicine.

1. Bhatt S, Gething PW, Brady OJ, et al. The global distribution and burden of dengue. Nature. 2013;496(7446):504-7. doi:10.1038/nature12060 · PMID 23563266

References

Sources cited on this page. PubMed links open the original abstract.

1. Bhatt S, Gething PW, Brady OJ, et al. The global distribution and burden of dengue. Nature. 2013;496(7446):504–507. PMID 23535579 · doi:10.1038/nature12060

The four dengue serotypes and why secondary infection is more dangerous

Dengue virus has four distinct serotypes (DENV-1 to DENV-4). After infection with one serotype, lifelong immunity to that serotype develops – but secondary infection with a different serotype can be significantly more severe. This is due to antibody-dependent enhancement (ADE): antibodies from the first infection bind to the second serotype but cannot neutralise it effectively. Instead, they facilitate entry of the virus into macrophages, dramatically increasing viral replication and the inflammatory response. This mechanism explains why dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) are predominantly seen in secondary infections or in infants with waning maternal dengue antibodies.

Clinical phases and monitoring schedule

Dengue follows a predictable three-phase clinical course, and blood monitoring must align with this timeline:

• Febrile phase (days 1–3): High fever (39–40°C), headache, retro-orbital pain, myalgia ("breakbone fever"). FBC shows progressive leucopenia. NS1 antigen is detectable and highly positive.
• Critical phase (days 3–7): The fever may defervese – creating a false sense of improvement – as plasma leakage from blood vessels begins. This is the most dangerous phase: rapid decline in platelets, rising haematocrit (haemoconcentration from plasma loss), and risk of dengue shock if leakage is severe. FBC should be monitored every 12–24 hours during this phase in hospitalised patients. Warning signs: abdominal pain, vomiting, clinical fluid accumulation, mucosal bleeding, lethargy, and rapid haematocrit rise of more than 20% above baseline.
• Recovery phase (days 7–10): Reabsorption of leaked plasma – haematocrit falls, urine output increases, and appetite returns. Platelet count recovers. This phase carries a risk of fluid overload if IV fluids were given liberally during the critical phase – bradycardia and a bradycardic rash are characteristic of recovery.

Management – no specific antiviral, meticulous supportive care

There is no approved antiviral treatment for dengue. Management is supportive and hinges on careful fluid balance:

• Oral rehydration is preferred in mild-to-moderate dengue to replace insensible losses without overloading the circulation
• IV crystalloid (normal saline or Ringer's lactate) is given in clinical deterioration – guided by haematocrit, urine output (target 0.5–1 mL/kg/hr), and clinical signs of shock
• Paracetamol for fever control – NSAIDs (ibuprofen, aspirin) are contraindicated because they impair platelet function and increase bleeding risk
• Platelet transfusion is generally reserved for platelets below 20 × 10⁹/L with active bleeding – prophylactic transfusion for thrombocytopenia alone is not routinely recommended by WHO, as platelets recover rapidly in recovery phase and transfusion carries risks