It may not be dengue
Early symptoms overlap with many infections. Geography, incubation time, exposures, rash, joint pattern and laboratory testing help separate them.
MalariaCOVID-19InfluenzaChikungunyaZikaRoss River virusJapanese encephalitisYellow feverMeaslesTyphoidLeptospirosisOther arboviruses
Fever after travel in a malaria area is urgent. Dengue and malaria often circulate in the same countries and even the same communities. Malaria can deteriorate quickly and needs prompt blood testing even if dengue, flu or COVID seems more likely. Co-infection is possible, so one positive test does not always end the investigation; one negative malaria test may also need repeating if suspicion remains.
Choose the test by day of illness
Days 0–7RT-PCR/NAAT detects viral RNA and can identify the serotype. NS1 antigen detects a dengue protein. A positive result confirms acute infection; a negative result does not completely exclude it.
After day 3IgM antibodies begin to appear. A single positive is usually presumptive because antibodies can cross-react with Zika, Japanese encephalitis, West Nile or yellow fever infection/vaccination.
After day 7IgM becomes the main test when early PCR/NS1 was missed or negative. Paired blood samples can clarify a changing antibody response.
Past infectionA single IgG test cannot reliably date an acute illness and may reflect old dengue or another flavivirus. Vaccine eligibility testing needs validated methods and clinical interpretation.
80–100%Reported Australian PCR sensitivity during the acute phase, with specimen timing and handling affecting results.
91% / 96%WHO review’s pooled sensitivity / specificity for combined NS1 + IgM ± IgG rapid tests against reference standards. Individual brands vary.
Home test?Rapid kits are sold online in some countries, but regulatory status and quality vary. In Australia, use clinician-ordered laboratory or approved point-of-care testing; do not rely on an imported retail kit to rule dengue in or out.
Rapid test positiveTalk to a doctor and confirm it
A positive NS1 result strongly supports current infection; an antibody-only result may need clarification. A clinician may order PCR/NS1 or serology plus a full blood count with platelets and haematocrit, and check liver, kidney and electrolyte results according to severity. Platelets often fall, but the trend and the whole clinical picture matter more than one number.
Rapid test negativeDo not ignore worsening illness
Testing too early or too late, low virus levels, secondary infection, poor sampling or test quality can produce a false negative. Seek medical review if fever persists, you feel worse, or exposure risk is meaningful. A clinician may repeat testing later or use a different method; urgent warning signs should never wait for another home test.
Just bitten?A dengue vaccine is not an emergency after-bite treatment
It cannot stop an infection from a bite that has already happened, and protection is not immediate. Qdenga is a planned two-dose course three months apart. If you develop fever or feel unwell, seek assessment and testing rather than rushing to vaccinate; vaccination is generally postponed during moderate or severe acute illness. Once recovered, discuss vaccination for future exposure with a qualified clinician.
