Dengue NS1 antigen
Detects a dengue virus protein in the blood during the first days of illness, which can show an early, current dengue infection.
AI-verified against cited sources. Awaiting expert reviewAlso called DENV NS1, Dengue NS1LOINC 91064-6
What it is
Dengue is a virus spread by Aedes mosquitoes, common in tropical and subtropical areas. There are four related types of the virus. NS1 is a protein the virus makes and releases into the blood while it is multiplying. The NS1 test looks for that protein, so it can show a current infection in the first days after symptoms start, before antibodies have formed. It is printed as positive or negative.
Why it matters
Early in dengue, antibody tests are often still negative, so NS1 or a PCR test is used to find the virus itself. CDC says NS1 tests can be as sensitive as molecular tests in the first 0-7 days of symptoms. A positive result helps your clinician confirm dengue and watch for warning signs. A negative result does not rule dengue out.
If it’s low
A negative NS1 does not rule out dengue. It can be negative if the sample was taken after the first week of illness, when NS1 fades, or if you were tested very early or have a different illness. Your clinician may repeat testing with PCR or an antibody test.
Common causes
- Not infected with dengue
- Sample taken after about day 7 of symptoms, when NS1 is no longer reliably detected
- A different illness with similar symptoms, such as another mosquito-borne virus
- A test kit that missed the infection
What can help
- Ask whether a PCR test or an IgM antibody test would add information
- Ask when and how to watch for warning signs if you were recently in a dengue area
If it’s high
A positive NS1 means the dengue virus protein was found in your blood, which usually points to a current dengue infection. It does not show how severe the illness will be. Most people with dengue have mild illness and get better in 1-2 weeks (WHO), but dengue can turn serious, so your clinician will tell you which warning signs to watch for.
Common causes
- A current dengue infection, usually in the first week of illness
What can help
- Talk with a clinician the same day about monitoring and care, especially for children, pregnant women and older adults
- Ask which warning signs mean you should go to urgent care
- Ask whether a confirmatory test, such as PCR, is needed
What can affect your result
- Day of illness: NS1 is detectable mostly in the first 0-7 days of symptoms
- Other illnesses: other mosquito-borne infections can look like dengue, and NS1 does not react with other flaviviruses of concern
- Where you were: dengue is common in tropical and subtropical areas, including parts of Asia and Latin America
- NS1 is best detected in the first 0-7 days of symptoms. After about day 7 the test may not work well, and a negative result does not rule out infection (CDC).
- NS1 antigen tests do not cross-react with other flaviviruses of concern, unlike antibody tests (CDC).
- No rapid dengue test that includes NS1 has US FDA approval, and the NS1 ELISA is the only dengue antigen test the FDA has approved (CDC).
The test works only during the early, acute phase of illness. Ask for it as soon as dengue is suspected, ideally in the first week of symptoms. NS1 is present in the blood only in the early, acute phase of dengue, mainly in the first week after symptoms begin.
When to talk to a clinician
If you have a fever and live in or recently traveled to a dengue area, contact a clinician. Go to urgent care or an emergency department right away for warning signs such as severe belly pain, vomiting that will not stop, rapid breathing, bleeding gums or nose, blood in vomit or stool, extreme thirst, pale or cold skin, restlessness or marked weakness.
Questions you could ask
- Which dengue tests make the most sense for how many days I have been ill?
- How should I be monitored, and which warning signs should send me to urgent care?
- Do you want to confirm this with a PCR test?
- Since NS1 can miss infection after the first week, should I have a PCR or IgM test?
Questions people ask
Does a negative NS1 mean I do not have dengue?
No. NS1 is mainly detectable in the first week of illness, and a negative result does not rule out infection, especially after day 7. Your clinician may order a PCR test or an IgM antibody test, depending on how many days you have been sick.
How is NS1 different from the dengue IgM and IgG tests?
NS1 looks for the virus's own protein, so it works early in illness. IgM and IgG are antibodies your body makes in response. IgM becomes detectable after about day 3 and can stay positive for roughly 3 months. IgG can reflect an old infection and is not used on its own to diagnose a current one.
Show the science and sources
For clinicians and researchers
NS1 is a conserved, secreted non-structural glycoprotein found in high concentration in serum during the viremic phase, measured by ELISA or rapid immunochromatographic kits. CDC reports that NS1 antigen tests can be as sensitive as molecular tests during the first 0-7 days of symptoms and may not be optimal after day 7, that a negative NS1 or NAAT does not rule out infection, that NS1 and NAAT do not cross-react with other flaviviruses of concern, and that no rapid diagnostic test that includes NS1 detection has FDA approval, while the NS1 ELISA is the only FDA-approved dengue antigen test. A 2026 review describes NS1 antigen and molecular assays as preferred in the early viremic phase (days 1-5) and antibody assays as more useful after day 5. For a patient in the first 7 days CDC advises a NAAT and an IgM test, or an NS1 antigen test and an IgM test; after day 7, IgM is the primary test. Most molecular tests also identify the infecting serotype (CDC). LOINC 91064-6 (presence, immunoassay) is the generic code; the rapid-test code is 75377-2.
LOINC 91064-6 (primary), 75377-2, 101206-1. Specimen: serum-or-plasma.
Sources
- Testing and Diagnosis of Dengue (clinical guidance), Centers for Disease Control and Prevention
- About Dengue, Centers for Disease Control and Prevention
- Dengue and severe dengue, World Health Organization
- History, Virology, Pathogenesis, Epidemiology, and Laboratory Diagnosis of Dengue Virus: A Focused Review, Cureus (2026)
- LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 91064-6), U.S. National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.