Why test for persistent fever?
For a fever lasting several days, a Complete Blood Count is the backbone test — it tracks platelets (important in dengue) and signs of infection. Depending on the timing and symptoms, dengue NS1, typhoid tests (Widal or Typhidot) and inflammatory markers like CRP are added.
Timing matters: dengue NS1 is most useful in the first week, while typhoid antibody tests are more reliable after a few days. Always follow your treating doctor's advice.