From the Research
Rapid flu tests typically show positive results for about 3-4 days after symptoms begin, though this can vary by individual, as supported by the most recent evidence 1. The test detects viral proteins in your nasal secretions, and as your body fights the infection, the amount of virus decreases, eventually becoming undetectable by the test.
- Children may test positive longer than adults, sometimes up to 7 days, because they tend to shed the virus for longer periods.
- The timing of the test matters significantly - testing too early (within the first 24 hours of symptoms) or too late (after 4-5 days) can lead to false negatives.
- Even after you stop testing positive, you may still be contagious for up to a week after symptoms appear.
- If you're taking antiviral medications like oseltamivir (Tamiflu), this might reduce the duration of positive test results by reducing viral shedding more quickly, as shown in a study comparing oseltamivir and zanamivir 2. However, the most recent and highest quality study 1 suggests that the use of rapid influenza A/B and RSV direct molecular assays can improve emergency department oseltamivir use in pediatric patients, highlighting the importance of accurate and timely testing in managing influenza.
- The study found that the use of the Simplexa FluA/B & RSV Direct Assay provided a turnaround time of 2 hours and led to more appropriate use of oseltamivir.
- The ease of use of this assay and quick turnaround time allows for prompt decision-making, which is essential for patient care and effective disease control during the influenza season.