Clinicians should consider dengue in patients with fever who live in or recently traveled to areas with dengue risk. Besides fever, common symptoms include a severe headache, pain behind the eyes, muscle and joint pain and a rash. Don't wait for test results to start appropriate care.
Before testing
Review the patient's:
- medical history;
- residence and recent travel;
- CDC travel notices about outbreaks;
- vaccination records, especially for dengue, yellow fever and Japanese encephalitis.
Which test, when
| Phase | Recommended testing |
|---|---|
| Acute — days 0–7 after symptoms begin | On serum (preferred): either a NAAT (such as RT-PCR) plus an IgM antibody test, or an NS1 antigen test plus an IgM test |
| Convalescent — after day 7 | If the acute sample was negative or unavailable: IgM antibody testing is the main test. Some patients may still be NAAT- or NS1-positive |
- NAAT detects dengue RNA in blood, serum or plasma — usually for the first 7 days — and most tests identify the serotype. A positive result needs no further confirmation.
- NS1, a viral protein in serum during the first 7 days, indicates current or recent infection; NS1 tests can be as sensitive as molecular tests early on. The NS1 ELISA is the only FDA-approved dengue antigen test; other commercial NS1 and rapid tests are research use only.
- IgM can identify most recent infections after day 3, and stays detectable for about 3 months, becoming less reliable over time. Run it on samples with negative NS1 and PCR results, especially after day 3.
- A negative NAAT or NS1 result does not rule out infection.
Interpreting results
| Result | Classification |
|---|---|
| Positive NAAT or NS1 | Confirmed acute dengue (meets the national case definition's confirmatory criteria) |
| IgM positive in a single sample | Presumptive, recent infection |
| IgM (or IgG) turns from negative to positive between a sample from the first 7 days and one taken after symptoms fade | Recent infection |
IgG testing on a single sample is not recommended for diagnosing acute dengue, since it can reflect past dengue or other flavivirus infections.
Cross-reactivity
IgM tests can cross-react with other flaviviruses such as Zika and West Nile. Plaque reduction neutralization tests (PRNT) can sort out false positives and sometimes identify the virus — though not always, especially in people exposed to more than one flavivirus or where dengue and Zika antibodies are common. Public health labs or CDC can advise when PRNT helps distinguish dengue from Zika, Japanese encephalitis, St. Louis encephalitis, West Nile and yellow fever. Current NAAT and NS1 tests don't cross-react with these viruses.
Special situations
- Pregnant patients with symptoms who live in or traveled to an area with Zika risk should also have molecular Zika testing.
- Management: watch for shock, and reduce complications from leaky blood vessels, plasma leakage and organ damage.
Reporting
Dengue is nationally notifiable: report all suspected cases to the state or local health department. Most state health departments and commercial labs offer testing, and CDC can confirm results on samples sent by state laboratories.
Sources
Based on "Clinical Testing Guidance for Dengue," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
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