What this test measures
Dengue IgG is the immunoglobulin-G antibody against dengue virus. It appears slowly in primary infection (from day 7–10) and persists for life as a marker of past dengue exposure.
In secondary dengue (re-infection with a different serotype), IgG rises rapidly and to high levels in the first few days of fever — often before IgM. High early IgG with active fever and positive NS1 strongly suggests secondary infection — which carries higher risk of dengue haemorrhagic fever and shock.
Why it matters
India has four co-circulating dengue serotypes (DENV-1 to DENV-4). Many adults have had at least one prior dengue infection — often subclinical. When they get reinfected with a different serotype, antibody-dependent enhancement makes secondary dengue more severe.
Dengue IgG is used to: (1) identify secondary infection during acute illness — high IgG with NS1+/IgM+ = secondary; (2) confirm past dengue exposure for epidemiological studies; (3) assess immunity status before any dengue vaccine consideration (Qdenga is recommended only in seropositive individuals). Routine IgG testing alone for past exposure is not common in clinical practice.
How to prepare
No fasting required. The test can be done at any time of day. Mention any prior dengue history and current fever symptoms.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Anti-Dengue IgG (Index / Reactive-Non-reactive)[1][2] | Reactive in past infection or secondary acute infection | Non-reactive — no past dengue exposure. In acute fever, suggests primary infection (if NS1/IgM positive). In dengue vaccine considerations, indicates the patient is seronegative — current dengue vaccines (Qdenga) are not recommended in seronegative individuals due to severe-dengue enhancement risk. | Reactive — past dengue infection or active secondary infection. In acute fever with positive NS1 or IgM, indicates secondary dengue — higher severe-disease risk. Months after recovery, simply indicates past exposure. |
Dengue IgG interpretation in clinical context
| Clinical setting | IgG result | Interpretation |
|---|---|---|
| Acute fever, NS1+, IgM+, IgG high | High | Secondary dengue — higher severity risk |
| Acute fever, NS1+, IgM+, IgG negative | Negative | Primary dengue |
| Convalescent, NS1−, IgM+, IgG rising | Positive | Resolving primary infection |
| Months after recovery | Positive | Past dengue exposure |
| Pre-vaccine assessment | Positive | Seropositive — Qdenga can be considered |
| Pre-vaccine assessment | Negative | Seronegative — Qdenga not recommended |
Frequently asked questions
What does it mean if my dengue IgG is positive?
In acute fever with positive NS1 or IgM, high IgG suggests secondary dengue — higher risk of severe disease, daily monitoring needed. Months after illness, it simply means past dengue exposure.
Why is secondary dengue more dangerous?
Antibodies from a previous dengue serotype can enhance entry of the new serotype into immune cells — a phenomenon called antibody-dependent enhancement. This drives the high viraemia and capillary leak seen in dengue haemorrhagic fever.
I have had dengue before — am I immune now?
You have lifelong immunity to the serotype you had, but only short-term (months) cross-protection to the other three serotypes. Reinfection is possible.
Should I get the dengue vaccine if my IgG is negative?
Current dengue vaccines (Qdenga, CYD-TDV) are recommended only in seropositive individuals. Seronegative recipients can have worse outcomes when subsequently infected. Decisions are individualised.
How long after dengue does IgG stay positive?
For life. IgG is a permanent marker of past dengue exposure.
Can IgG help with current fever diagnosis?
Alone, no — past-positive IgG does not confirm current dengue. In combination with NS1 and IgM, it helps identify secondary infection.
Should I be tested for IgG if I never had a known dengue episode?
Many people have had subclinical dengue and are IgG-positive without remembering. Routine testing is not needed unless for vaccine consideration or research.
Related Infectious Disease tests
Tests commonly ordered alongside DENGUE-IGG, or that help interpret an unexpected result.
Sources & references
- NIV Pune — Dengue · accessed 2026-05-30T00:00:00.000Z
- NCDC India — Dengue · accessed 2026-05-30T00:00:00.000Z
- WHO — Dengue Fact Sheet · accessed 2026-05-30T00:00:00.000Z
- ICMR India — Dengue Guidelines · accessed 2026-05-30T00:00:00.000Z
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