1. Overview
Dengue virus (DENV) is a mosquito-borne virus belonging to the Flaviviridae family and the Flavivirus genus. It is transmitted to humans primarily through the bite of Aedes aegypti mosquitoes. Dengue virus exists in four serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), and infection with any serotype can result in a wide spectrum of disease.
Dengue is a major public health problem in tropical and subtropical regions. Detection of Dengue-specific IgM and IgG antibodies plays a crucial role in diagnosing dengue infection, determining the stage of disease, and differentiating between primary and secondary infections.
2. Symptoms
Most dengue infections are asymptomatic. Symptomatic cases range from mild dengue fever (DF) to severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).
Typical clinical features include sudden onset of high fever, severe headache, retro-orbital pain, myalgia, arthralgia, gastrointestinal discomfort, and rash. Minor hemorrhagic manifestations such as petechiae, epistaxis, and gingival bleeding may occur.
Laboratory findings commonly include leukopenia, while thrombocytopenia may be observed, particularly in more severe cases. The World Health Organization classifies DHF into four grades (I–IV), with grades III and IV associated with shock.
3. Causes
This infection occurs following transmission of the virus by infected Aedes mosquitoes. After infection, the host’s immune system produces virus-specific antibodies.
- IgM antibodies appear first and indicate recent infection.
- IgG antibodies appear later and are associated with past exposure or secondary infection.
Secondary dengue infections are characterized by a rapid and high rise in IgG levels, which may be associated with hypersensitivity reactions and increased disease severity.
4. Risk Factors
Risk factors for this infection include residence in or travel to endemic regions, exposure to mosquito-infested environments, and lack of protective measures against mosquito bites.
Individuals with prior dengue infection are at increased risk of secondary infection, which may lead to more severe disease due to immune-mediated mechanisms. Children, elderly individuals, and patients with comorbid conditions may also experience more severe manifestations.
5. Prevention and Diagnostic Approach
This antibody testing is indicated in suspected dengue fever, especially after the acute phase.
Serological response:
- IgM antibodies generally become detectable 4–5 days after symptom onset, peak during the second week, and usually remain detectable for up to 12 weeks, though persistence may be longer.
- IgG antibodies rise around 7 days after infection, peak during the second week, and may persist for months to lifelong, particularly after secondary infections.
Primary vs secondary infection:
- Primary infection: Early IgM response with delayed IgG appearance
- Secondary infection: Rapid and high IgG response with weaker or absent IgM response
Methods of detection include:
- Immunochromatography (rapid tests)
- Enzyme-linked immunosorbent assay (ELISA)
- Enzyme-linked fluorescent assay (ELFA)
- Chemiluminescent microparticle immunoassay (CMIA)
Sample collection:
- Collect 2.0 ml of blood in a plain (red-capped) or EDTA (lavender-capped) tube
- Either whole blood or serum can be used
Rapid test interpretation:
- Negative: Control line only
- IgM positive: Control + IgM line
- IgG positive: Control + IgG line
- IgM & IgG positive: Control + both IgM and IgG lines
- Invalid: No control line present
ELISA interpretation:
Dengue IgM/IgG units are calculated as:
Units = Sample Optical Density × 10 / Cut-off value
- IgM: <9 negative, 9–11 equivocal, >11 positive
- IgG: <18 negative, 18–22 equivocal, >22 positive
Paired serology (acute and convalescent samples collected 10–14 days apart) may be required to confirm recent infection by demonstrating rising antibody titers.
Clinical Significance
Dengue IgM and IgG antibody testing is a cost-effective and widely used diagnostic tool. It helps confirm this infection, determine the phase of illness, and differentiate between primary and secondary infections.
While antibody testing is valuable, results must be interpreted alongside clinical findings and the timing of sample collection, as early testing may yield false-negative results. Proper interpretation supports timely patient management and helps reduce complications associated with severe dengue.
