Hi, Thank you for your query, The test used to detect Typhoid usually is Widal test which is an indirect test, by measuring the antibodies produced in our body against the salmonella. And the antibiotics will persist longer even if the infection has been treated effectively and they show anamnestic reaction means these antibodies will raise due to other infections like dengue, viral fevers. So if we do typhoid test(widal test), as it measures the antibodies show positive in spite of there is no current infection and fever clinically. In this situation interpretation of the report by the doctor is important in correlating with clinical findings. Hope I have answered your query.