Dengue IgM Antibody
Dengue IgM· also: Anti-Dengue IgM, DENV IgM
Clinical Overview
Dengue IgM antibody appears 4–5 days after the onset of dengue fever and persists for 2–3 months. A positive IgM indicates recent dengue infection and is the test of choice after Day 5 of fever when NS1 antigen has already been cleared. Dengue IgM serology complements NS1 testing to ensure accurate diagnosis throughout the course of dengue illness.
Why This Test Matters
Dengue IgM is the primary serological marker for recent/current dengue. Because many dengue infections occur in settings where PCR is unavailable, IgM serology combined with NS1 antigen testing is the standard WHO-recommended diagnostic approach. IgM serology is especially critical for late presenters (after Day 5) and for retrospective diagnosis of dengue after the acute febrile phase. Cross-reactivity with other flaviviruses (Zika, West Nile, Japanese encephalitis, and Yellow Fever vaccine) is a known limitation — particularly in endemic regions with multiple circulating flaviviruses. During a secondary dengue infection (second exposure to a different dengue serotype), IgG rises rapidly (anamnestic response) and IgM may be lower or absent — a high IgG:IgM ratio suggests secondary infection, which carries higher risk of severe dengue (DHF/DSS).
Reference RangesWHO/IFCC standards
| Reference Range | Unit | Notes |
|---|---|---|
| Negative / Non-reactive | qualitative | Negative = no recent infection; Positive = recent dengue |
Also reported in: index value.
What Causes Abnormal Results?
High Dengue IgM Causes
- Active dengue infection (detectable from Day 4–5 of fever)
- Recent dengue infection (persists for 2–3 months after recovery)
Low Dengue IgM Causes
- Testing too early (Day 1–3 of fever — NS1 is positive before IgM appears)
- Secondary dengue (IgM may be low/absent; IgG rises much faster and higher)
- Immunocompromised patients may have blunted IgM responses
Signs & Symptoms to Watch For
How to Prepare for This Test
Dengue IgM is best tested from Day 5 onwards after fever onset. Collect a convalescent serum sample if initial testing (Day 1–4) was done. For comprehensive dengue diagnosis, request NS1 (for early illness) AND IgM/IgG (for later illness or confirmation).
Factors That Can Affect Results
- Cross-reactivity with other flaviviruses: Zika, West Nile, Yellow Fever, Japanese Encephalitis — all can produce positive dengue IgM in some assays
- Vaccination for Yellow Fever or Japanese Encephalitis can cause a positive dengue IgM on some assays
- Secondary dengue infection: IgM is low/absent; IgG predominates
- Sample hemolysis can affect some ELISA-based dengue assays
Related Topics
Frequently Asked Questions
What is the difference between dengue NS1 and dengue IgM — when should each be used?
NS1 antigen tests detect the virus itself (not the immune response) and are positive from Day 1 to Day 5. Dengue IgM detects the patient's immune response and appears from Day 4–5, remaining positive for 2–3 months. For best sensitivity: use NS1 if the patient has had fever for 5 days or less. Use IgM if fever has lasted more than 5 days. If clinical suspicion remains, order both tests together regardless of fever duration — a positive either test (or both) confirms dengue.
Can I have dengue again after recovering once?
Yes. There are four dengue serotypes (DENV 1–4). Infection with one serotype gives lifelong immunity against that serotype only, but prior infection actually increases the risk of severe dengue (hemorrhagic fever/shock) if infected with a different serotype. This is due to antibody-dependent enhancement (ADE) — pre-existing cross-reactive antibodies from the first infection can actually help the second serotype infect more cells. Secondary dengue infections are generally more severe than primary infections. People who have had dengue should be especially cautious about mosquito protection.