What is Dengue Fever?
Dengue fever is a mosquito-borne viral infection caused by four closely related dengue virus serotypes (DENV-1 through DENV-4) of the genus Flavivirus. It is transmitted primarily by the day-biting Aedes aegypti mosquito, with Aedes albopictus serving as a secondary vector. Dengue is now the most common vector-borne viral infection in tropical and subtropical regions worldwide, with over 100 countries affected across Southeast Asia, the Western Pacific, the Americas, and Africa.
Epidemiology in Thailand
Thailand remains one of the countries most heavily affected by dengue fever in Southeast Asia. As of March 2023, dengue is endemic in more than 100 countries, and the Americas, Southeast Asia, and the Western Pacific regions are the most seriously affected. Thailand reports tens of thousands of dengue cases annually, with significant seasonal variation. The rainy season from May through October creates ideal breeding conditions for Aedes mosquitoes, leading to dramatic surges in cases during these months.
In Pattaya and surrounding Chonburi Province, dengue activity has historically been elevated due to the warm tropical climate, urban density, and tourism-related population movement. Dengue fever acquired in Southeast Asia typically presents with more severe hemorrhagic symptoms compared to infections acquired elsewhere, and cases can progress to dengue hemorrhagic fever or dengue shock syndrome.
Symptoms: What to Watch For
The incubation period after a dengue mosquito bite is typically 4 to 7 days, with symptoms lasting 2 to 7 days. Most infected individuals are asymptomatic or have only mild symptoms, but about 20% develop noticeable illness. The classic presentation includes:
• Sudden high fever: Typically 40°C (104°F), often lasting 2 to 7 days
• Severe headache: Especially pain behind the eyes (retro-orbital pain), which is characteristic of dengue
• Severe muscle and joint pain: So severe that dengue was historically called “breakbone fever”
• Nausea and vomiting: Common during the febrile phase
• Rash: A macular or maculopapular rash that typically appears a few days after fever onset, involving the trunk and spreading outward
• Mild bleeding: Nosebleeds, gum bleeding, or easy bruising
• Fatigue and malaise: Profound tiredness that can persist for weeks
Most patients recover fully within a week or so, though convalescence can be prolonged, with fatigue and weakness lasting several weeks.
Dengue Hemorrhagic Fever and Warning Signs
Secondary infection with a different dengue serotype carries a significantly higher risk of severe disease due to antibody-dependent enhancement. The World Health Organization now uses an updated classification system that identifies patients with dengue who have warning signs requiring careful observation:
• Abdominal pain or tenderness
• Persistent vomiting
• Clinical fluid accumulation (abdominal distension, difficulty breathing)
• Mucosal bleeding
• Lethargy or restlessness
• Liver enlargement greater than 2 centimeters below the right costal margin
• Laboratory findings: increase in hematocrit greater than 20% of baseline with a rapid decrease in platelet count
Without prompt fluid resuscitation, patients who progress to dengue shock syndrome can die within 12 to 24 hours. However, with appropriate hospital care, mortality is less than 1%.
Diagnosis
Early diagnosis (days 1 to 5 of illness) relies on:
• NS1 antigen detection: Rapid antigen-based ELISA tests that can identify dengue virus non-structural protein 1 during the acute phase
• RT-PCR: Reverse transcription polymerase chain reaction, the gold standard for detecting dengue viral RNA during the first week of illness
After day 5, diagnosis shifts to serology:
• Dengue IgM ELISA: Becomes positive after 4 to 5 days of illness
• Dengue IgG ELISA: Indicates past infection or secondary infection
Common laboratory findings include leukopenia (low white blood cell count), thrombocytopenia (platelet count below 100,000), and modest elevations of serum AST (aspartate aminotransferase) without significant liver synthetic dysfunction.
Treatment
There is no specific antiviral treatment for dengue. Management is entirely supportive:
• Adequate hydration: Oral or intravenous fluids are the cornerstone of dengue management. Patients should drink plenty of fluids to maintain hydration and prevent shock from plasma leakage.
• Paracetamol (acetaminophen): The recommended antipyretic for fever and pain relief. NSAIDs (ibuprofen, aspirin, diclofenac) should be avoided until dengue has been ruled out, as they increase the risk of bleeding.
• Close monitoring: Patients with warning signs should be hospitalized for serial hematocrit measurements, platelet counts, and clinical observation.
• Blood transfusion: May be needed in severe dengue with significant bleeding or profound thrombocytopenia.
Prevention
There is currently no universally available dengue vaccine, although several vaccines are in use in various countries. The most effective prevention strategies focus on mosquito control and personal protection:
• Eliminate breeding sites: Empty, cover, or treat any container that collects standing water around the home — flower pots, buckets, discarded tires, water storage containers, and roof gutters
• Use mosquito repellent: DEET-containing repellents applied to exposed skin
• Wear protective clothing: Long sleeves and long pants, especially during daytime when Aedes mosquitoes are most active
• Install window screens: Use screens on doors and windows, or sleep under insecticide-treated bed nets
• Community action: Support local mosquito control programs and fogging operations
Dr. Kijakarn notes that dengue is particularly dangerous in Pattaya due to its high tourism volume. “Many tourists are not aware of dengue risk and do not take prevention measures seriously. We see adults and children alike presenting with severe dengue during the rainy season. Anyone visiting or living in tropical Thailand should treat dengue prevention with the same seriousness as malaria prevention.”
This article is for general information only and does not replace professional medical advice. If you are experiencing symptoms, please consult a healthcare provider.
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