Dengue: A Complete Medical Guide — Symptoms, Transmission, Diagnosis, Treatment and Prevention
Dengue is a mosquito-borne viral infection that affects an estimated 100–400 million people yearly worldwide. This comprehensive guide explains how dengue spreads, the clinical phases of illness, hallmark symptoms, how clinicians diagnose it, the difference between classic dengue and severe dengue, available treatments, and the most effective prevention strategies.
What is dengue?
Dengue is an acute viral infection caused by four distinct serotypes of the dengue virus: DENV-1, DENV-2, DENV-3, and DENV-4. It is transmitted through the bite of infected female Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus. These mosquitoes are primarily active during the day and thrive in tropical and subtropical regions worldwide.
Dengue presents along a clinical spectrum ranging from asymptomatic infection and mild flu-like illness to severe dengue, a medical emergency that can result in shock, internal bleeding, and multi-organ failure. Because there is no specific antiviral cure, early clinical evaluation and optimized supportive care are crucial for reducing morbidity and mortality.
How common is dengue and who is at risk?
Dengue is one of the fastest-spreading mosquito-borne diseases in the world. According to global health estimates:
- Over 100–400 million infections occur each year.
- Approximately half of the world’s population lives in areas at risk.
- Tropical and subtropical countries in Asia, Latin America, Africa, and the Caribbean have the highest burden.
Risk factors for dengue include:
- Living or traveling in dengue-endemic regions.
- Residing in urban or periurban environments where Aedes mosquitoes thrive.
- Exposure to areas with standing water (ideal for mosquito breeding).
- Lack of mosquito control programs or poor sanitation.
- Prior dengue infection, which increases risk of severe disease with a different serotype.
Causes and transmission of dengue
Dengue is caused by infection with one of four dengue virus serotypes (DENV-1 to DENV-4). A person who recovers from one serotype gains lifelong immunity to that specific serotype but only partial and temporary protection against the others. Subsequent infections with different serotypes increase the risk of developing severe dengue.
How dengue is transmitted
The main route of transmission is through the bite of an infected Aedes mosquito. Key points include:
- Daytime biting: Aedes mosquitoes are most active in the early morning and late afternoon.
- Urban breeding: They breed in clean, stagnant water found in buckets, plant pots, containers, gutters, tires, and water storage tanks.
- Human–mosquito–human cycle: Mosquitoes become infected when they feed on a person with dengue and then transmit the virus to other individuals.
Other rare routes
- Vertical transmission (pregnant person to fetus).
- Blood transfusions from infected donors (rare but documented).
- Organ transplantation (extremely rare).
Symptoms and clinical presentation
Dengue manifests in three clinical phases: febrile, critical, and recovery. The severity ranges widely, and not all patients progress through all stages.
1. Febrile phase (day 1–3)
This stage includes sudden-onset high fever and systemic symptoms:
- High fever (often 39–40°C / 102–104°F)
- Severe headache
- Pain behind the eyes (retro-orbital pain)
- Muscle and joint pain (“breakbone fever”)
- Nausea and vomiting
- Fatigue and weakness
- Skin rash (may appear early or later)
Some people may have minor bleeding signs such as gum bleeding or nosebleeds.
2. Critical phase (day 3–7)
As fever drops, some patients improve, but others develop warning signs indicating risk of severe dengue. Plasma leakage may occur, which can lead to shock if not managed promptly.
Warning signs include:
- Severe abdominal pain or persistent vomiting
- Rapid breathing or difficulty breathing
- Bleeding manifestations (nose, gums, bruising)
- Restlessness or lethargy
- Enlarged liver
- Clinical fluid accumulation (ascites, pleural effusion)
- Drop in platelet count with rising hematocrit
3. Recovery phase (day 7–10)
Patients gradually improve as fluids return to the bloodstream. Clinical signs include:
- Gradual recovery of appetite
- Improved hemodynamic stability
- Rash may reappear (“white islands in a sea of red” pattern)
- Generalized itching (common)
When to see a doctor — warning signs
Seek urgent or emergency medical care if experiencing:
- Severe abdominal pain
- Persistent vomiting
- Bleeding from gums or nose
- Blood in vomit or stool
- Difficulty breathing
- Extreme restlessness or confusion
- Cold, clammy skin or signs of shock
Infants, pregnant people, older adults, and individuals with chronic diseases should seek medical evaluation early in the illness.
How dengue is diagnosed
Dengue diagnosis is based on symptoms, travel history, physical exam, and laboratory tests.
Clinical evaluation
- Fever pattern and duration
- Warning signs assessment
- Hydration status and vital signs
- Presence of rash or bleeding
Laboratory tests
- NS1 antigen test: Detects the virus early (days 1–5).
- RT-PCR: Identifies viral RNA; confirms the serotype.
- IgM/IgG antibody testing: Useful later in the illness.
- Complete blood count (CBC): Used to monitor platelet count and hematocrit.
- Liver function tests: May show elevated enzymes.
Treatment: Evidence-based approach
There is no specific antiviral treatment for dengue. Management focuses on early detection of complications, careful monitoring, and maintaining adequate hydration.
Mild dengue (outpatient care)
- Hydration: Oral rehydration solutions, water, broth, electrolyte drinks.
- Fever and pain management: Acetaminophen (paracetamol) is recommended.
- Avoid aspirin and NSAIDs: They increase bleeding risk.
- Rest and nutrition: Light meals and adequate sleep support recovery.
Moderate to severe dengue (hospital care)
- Intravenous fluids: Carefully monitored to prevent shock or fluid overload.
- Close monitoring: Platelet count, hematocrit, urine output, vital signs.
- Management of bleeding: Medical interventions if significant bleeding occurs.
- Oxygen therapy: For respiratory distress.
- Intensive care: For shock, organ failure, or severe complications.
Home care and symptom relief
People with mild dengue can safely recover at home with proper care:
- Drink fluids regularly — dehydration is a major risk in dengue.
- Monitor warning signs — especially around the time the fever subsides.
- Use mosquito repellent to prevent spreading dengue to others.
- Eat soft, nutrient-rich foods to maintain strength.
- Rest often — fatigue may last for weeks.
Prevention strategies
Preventing dengue relies on reducing mosquito populations, preventing mosquito bites, and implementing public health measures.
Mosquito bite prevention
- Use EPA-registered insect repellents.
- Wear long-sleeved shirts and pants.
- Use mosquito nets if sleeping during the day.
- Install window and door screens.
Eliminating mosquito breeding sites
- Empty standing water from containers each week.
- Cover water storage tanks.
- Clean gutters and drainage areas.
- Dispose of old tires, bottles, and unused containers.
Vaccination
A dengue vaccine exists but is recommended only for certain populations depending on prior infection status, age group, and regional guidelines. Vaccination policies vary by country.
Complications and when dengue is serious
Severe dengue is a life-threatening condition and requires immediate medical attention. It includes:
- Dengue shock syndrome: dangerous drop in blood pressure due to plasma leakage.
- Severe bleeding: gastrointestinal bleeding, heavy mucosal bleeding.
- Severe organ impairment: liver failure, heart involvement, impaired consciousness.
- Fluid accumulation: pleural effusion or ascites.
Special considerations: children, elderly and pregnant individuals
Children
Children may develop severe dengue more quickly and may show atypical symptoms such as drowsiness, irritability, or decreased urine output. Early evaluation is essential.
Elderly adults
Older adults often have comorbidities such as diabetes, hypertension, or heart disease, increasing their risk of complications. Close monitoring is recommended.
Pregnancy
Dengue in pregnancy increases the risk of premature birth, hemorrhage, and, rarely, vertical transmission. Pregnant individuals should be monitored by a healthcare professional throughout the illness.
Frequently Asked Questions (FAQs)
Is dengue contagious?
Dengue is not spread directly from person to person. It requires a mosquito to transmit the virus. However, if a mosquito bites an infected person, it can transmit dengue to others.
Can you get dengue more than once?
Yes. There are four dengue serotypes. Infection with one provides lifelong immunity against that specific serotype but not the others. Subsequent infections increase the risk of severe dengue.
How long does dengue last?
Most dengue cases last 7–10 days, though fatigue and weakness may persist for weeks after the illness.
What should I avoid if I have dengue?
Avoid aspirin, ibuprofen, and other NSAIDs due to increased bleeding risk. Avoid dehydration and strenuous activity during the acute phase.
Practical tips and clinical takeaways
- Dengue is a viral infection without a specific cure — early supportive care saves lives.
- Monitor for warning signs when fever begins to drop.
- Hydration is a cornerstone of treatment in mild to moderate cases.
- Eliminating mosquito breeding sites is essential for prevention.
- Seek urgent care for severe abdominal pain, vomiting, bleeding, or signs of shock.
References & further reading
Sources include the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), Pan American Health Organization (PAHO), and peer-reviewed medical journals. For individualized advice, consult your healthcare provider.
