Dengue NS1 Antigen & IgG/IgM is a blood test used to help detect infection with the dengue virus (often called breakbone fever because of the severe body and joint aches it can cause). It combines two types of dengue testing in one report:

1) NS1 antigen — NS1 is a protein made by the dengue virus. If NS1 is detected, it usually means the virus is currently present in the bloodstream, most often in the early phase of illness.

2) Dengue antibodies (IgM and IgG) — These are proteins made by your immune system in response to dengue infection.

• IgM positive typically suggests a recent or current dengue infection (often appears a few days after fever begins).
• IgG positive may suggest past exposure to dengue or a later stage of infection; it can also rise quickly in a repeat (secondary) dengue infection.

How results are commonly interpreted (in plain language):

• NS1 positive: strong evidence of early dengue infection.
• NS1 negative, IgM positive: may indicate dengue infection that is a bit later (after the very early window), though timing matters.
• IgG positive only: can indicate past dengue infection or immunity from prior exposure; sometimes may reflect a later phase or secondary infection depending on symptoms and timing.
• All negative: dengue is less likely, but very early testing or testing late in illness can still yield negatives; repeat testing or additional tests may be needed if suspicion remains high.

This is a screening and diagnostic aid. Your clinician may interpret it along with your day of illness, symptoms, physical exam, local dengue activity, and other blood tests (such as platelet count and hematocrit) to assess severity and guide care.

This test is commonly ordered when someone has symptoms consistent with dengue, especially after being in or living in an area where dengue is circulating (often tropical/subtropical regions, during monsoon or warm seasons, or during local outbreaks). Dengue is spread by Aedes mosquitoes, so risk increases with mosquito exposure.

Typical reasons a doctor may order dengue NS1 and dengue antibody testing include:

• Acute fever (often sudden onset) with severe body aches or “breakbone” pain
• Severe headache and/or pain behind the eyes
• Joint and muscle pain, marked fatigue, chills
• Nausea, vomiting, loss of appetite, abdominal discomfort
• Skin rash that may appear a few days into illness
• Easy bruising, gum/nose bleeding, or other bleeding signs (warning features)
• Concern for low platelet count (thrombocytopenia) or rising hematocrit on a CBC during a febrile illness
• Illness after recent travel to dengue-endemic regions or close contact with an outbreak area

Timing matters for accuracy: dengue NS1 antigen is most useful early in infection, while IgM/IgG dengue antibody testing becomes more informative as the immune response develops. If testing is done very early (or sometimes later), your clinician may recommend repeating the test or adding other studies to confirm the diagnosis.

This test can also help distinguish dengue from other causes of fever (such as viral flu-like illnesses or other mosquito-borne infections). However, results can sometimes be affected by cross-reactivity with related viruses in the same family in certain settings, so clinical correlation is important.

• Dengue fever (classic dengue / breakbone fever)
• Severe dengue (including dengue hemorrhagic fever and dengue shock syndrome)
• Secondary (repeat) dengue infection
• Acute undifferentiated febrile illness in dengue-endemic areas (evaluation for dengue as a cause)
• Post-travel fever (assessment for dengue among other infections)

• Early detection of dengue virus infection to support timely medical care
• Safe fever evaluation and decision-making (e.g., when to seek urgent care, hydration plans, monitoring)
• Reducing complications by identifying dengue and guiding appropriate follow-up (especially when platelet counts may drop)
• Public health and outbreak awareness by confirming dengue in symptomatic individuals
• Travel and mosquito-borne illness assessment after trips to dengue-risk regions