Dengue IgM Antibody
Dengue IgM antibody is produced by the body in response to dengue virus infection. It becomes detectable around day 4–5 of fever, peaks at day 10–14, and can persist for 2–3 months. IgM is the most useful serological test after the first week of illness, when NS1 sensitivity drops. A positive IgM with compatible fever indicates recent dengue infection.
Expected Result
Normal
Negative
Best tested from day 5 of fever onwards. Cross-reactivity with other flaviviruses can produce false positives.
This is a qualitative test — results are reported as positive or negative rather than as a numeric range. Interpretation may vary by laboratory method; always review with your doctor.
What a Negative Result Means
A negative dengue IgM in the first 3 days of fever is expected because antibodies have not yet developed — use NS1 instead. A persistently negative IgM after day 7 of fever makes dengue unlikely. Other causes of acute febrile illness (malaria, typhoid, scrub typhus, leptospirosis, chikungunya) should then be considered.
What a Positive Result Means
A positive dengue IgM indicates recent dengue infection — typically within the last 2–3 months. In a patient with compatible fever, it is diagnostic. Cross-reactivity with other flaviviruses (Zika, Japanese encephalitis, yellow fever) and chikungunya can cause false positives. Persistent IgM can occasionally last 6+ months and should be interpreted cautiously in patients with new unrelated illness.
Frequently Asked Questions
When is the best time to test dengue IgM?
From day 5 of fever onwards. Before day 5, IgM sensitivity is low and NS1 is the test of choice. Between day 5–10, combining NS1 and IgM gives the best diagnostic yield. After day 10, IgM plus IgG is most informative — especially to distinguish primary from secondary dengue.
What is the difference between primary and secondary dengue?
Primary dengue is a first infection with any dengue serotype — produces a strong IgM with weak IgG. Secondary dengue is re-infection with a different serotype — produces a stronger IgG response (sometimes higher than IgM) and is associated with higher risk of severe dengue and dengue hemorrhagic fever. The IgM:IgG ratio helps distinguish them.
Can dengue IgM cross-react with other infections?
Yes. Cross-reactivity with other flaviviruses (Japanese encephalitis, Zika, yellow fever) and sometimes with chikungunya can produce false positives. In patients who have received yellow fever or Japanese encephalitis vaccine, dengue IgM interpretation is complicated. Clinical context and NS1/PCR when available reduce this uncertainty.
Related Infectious tests
See all →ASO Titre (Anti-Streptolysin O)
Antibody against streptococcal toxin — evidence of recent strep infection.
IU/mLInfectiousWidal Test
Antibody test for typhoid fever — used cautiously due to specificity issues.
InfectiousDengue NS1 Antigen
Early dengue virus antigen — detectable in the first week of fever.
InfectiousDengue IgG Antibody
Antibody marking past or long-term dengue infection.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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