Most people will test positive on a rapid antigen test for about 10 to 14 days after symptoms start, though some test positive for longer. Lab-based PCR tests can stay positive much longer, sometimes up to 90 days, even when you’re no longer contagious. How long your tests stay positive depends on the type of test, the severity of your illness, and your immune system.
Rapid Tests vs. PCR Tests
The two main COVID test types detect different things, and that distinction matters a lot for how long each one stays positive.
Rapid antigen tests (the at-home kind) detect proteins from actively replicating virus. They generally turn negative sooner because once the virus stops multiplying in large quantities, there isn’t enough protein to trigger a result. For most people with mild to moderate illness, rapid tests turn negative within about two weeks of symptom onset, though individual variation is common.
PCR tests (also called NAAT tests) are far more sensitive. They detect tiny fragments of viral genetic material, and those fragments can linger in your nose and throat long after the live virus is gone. The CDC notes that these tests may continue to show a positive result for up to 90 days. That doesn’t mean you’re still sick or contagious. It means the test is picking up leftover debris from an infection your body has already cleared. The median time to a negative PCR result in studies of earlier coronavirus strains was about 30 days, with a range stretching from as few as 2 days to as many as 81.
When You First Test Positive After Exposure
If you’ve been exposed to someone with COVID but don’t have symptoms yet, the FDA recommends waiting at least 5 full days after exposure before testing. Testing too early often produces a false negative because the virus hasn’t replicated enough to be detectable. If symptoms appear before that 5-day mark, testing at symptom onset is reasonable. Rapid tests are most reliable when taken during the first few days of noticeable symptoms, when viral levels in the nose are highest.
What the Current Isolation Guidelines Say
As of 2024, the CDC no longer recommends a fixed 5- or 10-day isolation period for COVID. Instead, the guidance aligns COVID with other respiratory viruses: stay home while you’re sick, and return to normal activities once your symptoms have been improving for at least 24 hours and any fever has been gone for a full day without fever-reducing medication.
After you resume normal activities, the CDC encourages five additional days of precautions: wearing a well-fitting mask around others, improving ventilation, keeping some distance, and practicing good hand hygiene. This buffer period accounts for the fact that some people still shed lower levels of virus even as they feel better.
Why Some People Test Positive Longer
Severity of illness is one of the biggest factors. People who were sicker tend to have higher viral loads and shed virus for a longer stretch. Older adults and those with weakened immune systems also tend to stay positive longer on both test types.
Research published in The Lancet Microbe found that among immunocompromised patients, about 25% were still PCR-positive 21 days or more after their initial detection. People with certain immune conditions tested positive even longer. Those with B-cell disorders (which impair antibody production), organ transplant recipients on immune-suppressing drugs, and people living with uncontrolled HIV all had significantly extended durations of infection. In one extreme case, a participant with advanced AIDS remained positive for over 200 days. For most transplant recipients, though, infection resolved within 56 days.
For the average healthy adult, a lingering positive rapid test beyond two weeks is uncommon but not alarming. A lingering positive PCR test beyond two weeks is quite common and rarely means you’re still infectious.
Paxlovid Rebound and Retesting Positive
Some people who take the antiviral Paxlovid experience what’s called “rebound,” where symptoms and a positive test return after an initial improvement. A Harvard Medical School analysis found that about 1 in 5 people (20.8%) who took Paxlovid experienced virologic rebound, compared to just 1.8% of those who didn’t take the drug. If you’ve finished a course of Paxlovid and test negative, then test positive again a few days later with returning symptoms, this rebound pattern is a likely explanation. Rebound cases are generally mild, but you should consider yourself contagious again while testing positive.
Practical Testing Advice
If you’re testing to decide whether you’re safe to be around others, rapid antigen tests are more useful than PCR tests. A positive rapid test suggests you likely still have enough active virus to be contagious. A negative rapid test, especially two negatives taken 48 hours apart, is a strong signal that your contagious window has closed.
Avoid getting a PCR test in the weeks after recovery just to “confirm” you’re negative. Because PCR results can stay positive for up to three months, a positive result will be difficult to interpret and may cause unnecessary anxiety or complications with travel, work, or school policies. If you need documentation of recovery rather than a current negative test, a note from a healthcare provider along with the date of your original positive result is typically more useful than repeat testing.