How long can you test positive for COVID-19 (Coronavirus Disease 2019) on rapid testing after an acute infection?

How Long Can You Test Positive for COVID-19 on Rapid Testing After an Acute Infection?

Individuals can test positive on COVID-19 rapid antigen tests for up to 5-10 days after symptom onset, with approximately 80% of symptomatic individuals still testing positive at day 5 after symptom onset. 1

Rapid Antigen Test Positivity Duration

Rapid antigen tests detect viral proteins and primarily indicate active infection with sufficient viral load. The duration of positivity varies based on several factors:

• Symptomatic individuals:

  • Approximately 80.2% of symptomatic individuals still test positive 5 days after symptom onset 1
  • Positivity rates decline significantly after 7 days from symptom onset 2
  • Testing sensitivity is highest (89%) within the first 5 days of symptoms 3
  • After 5 days, sensitivity drops to approximately 54% 4

• Asymptomatic individuals:

  • Lower overall test sensitivity (63%) compared to symptomatic individuals 3
  • Positivity duration is typically shorter than in symptomatic cases

Factors Affecting Test Positivity Duration

Several factors influence how long you may test positive after infection:

• Viral load: Higher viral loads correlate with longer periods of test positivity
• Symptom severity: More severe symptoms often correlate with higher viral loads and longer test positivity
• Vaccination status: Vaccinated individuals may clear the virus more quickly
• Variant type: Different variants may have different patterns of viral shedding, though studies show similar detection rates between Omicron and pre-Omicron variants 5

Clinical Implications

The persistent positivity on rapid antigen tests has important implications:

1. Isolation decisions: The high rate of continued positivity at day 5 supports guidelines requiring a negative test to end isolation 1

2. Return to work/school: A positive rapid antigen test, even after symptoms improve, suggests potential ongoing infectiousness

3. Distinguishing from PCR: Unlike PCR tests which can remain positive for weeks or months due to detection of non-viable viral RNA, antigen tests generally correlate better with potential infectiousness

Common Pitfalls in Interpreting Test Results

• False negatives: More common after 7 days of symptoms when viral loads decrease
• Premature testing: Testing too early after exposure (before day 5) may yield false negatives
• Improper sample collection: Can significantly reduce test sensitivity
• Misinterpreting faint lines: Even faint positive lines should be considered positive results

Testing Recommendations

• For optimal detection, perform rapid antigen testing within the first 5 days of symptom onset 3
• If clinical suspicion remains high after a negative rapid test, confirm with a nucleic acid amplification test (NAAT) 3
• When using rapid tests to determine isolation duration, testing at day 5 or later provides more reliable information about potential ongoing infectiousness 1

Remember that a positive rapid antigen test generally indicates the presence of viable virus and potential infectiousness, while a negative test after symptoms resolve suggests lower risk of transmission.