How long you test positive for COVID-19 depends almost entirely on which type of test you use. A rapid antigen test typically turns negative within 7 to 10 days of your first symptoms, while a PCR test can stay positive for up to 90 days. That gap matters because the two tests detect different things, and a positive result doesn’t always mean you’re still contagious.
Rapid Antigen Tests: 5 to 10 Days
Rapid antigen tests detect proteins on the surface of active virus particles, which makes them a better gauge of whether you’re currently infectious. Most people will test positive on a rapid test for roughly a week after symptoms start, though the exact timeline varies.
A CDC study during the Omicron wave tracked hundreds of people with confirmed infections and found that on day 5 after symptom onset, about 68% still tested positive on a rapid antigen test. By day 6, that dropped to 55%. On day 7, it was 52%, and by days 8 and 9, around 38 to 39% were still testing positive. People with symptomatic infections stayed positive longer than those without symptoms. At day 5, nearly 80% of symptomatic people still had a positive rapid test, compared to a much smaller share of asymptomatic cases.
The practical takeaway: if you’re using rapid tests to decide when you’re no longer contagious, expect to keep testing positive for at least 5 to 7 days, and possibly up to 10 or beyond if your symptoms were more significant.
PCR Tests: Up to 90 Days
PCR tests are far more sensitive than rapid tests. They amplify tiny fragments of viral genetic material, which means they can pick up traces of the virus long after your body has cleared the actual infection. The CDC explicitly notes that people may have detectable viral RNA and test positive on a PCR test for up to 90 days after their initial positive result. For this reason, the CDC recommends against using PCR tests to re-check someone who has tested positive in the last 90 days, since the result is likely to be misleading.
This doesn’t mean you’re sick or contagious for three months. It means the test is picking up leftover genetic fragments that your immune system hasn’t fully cleared yet.
Why PCR Tests Stay Positive So Long
Researchers at MIT’s Whitehead Institute discovered a surprising reason for these lingering positive results. Small pieces of the virus’s genetic code can actually get inserted into the DNA of human cells through a process involving structures called retrotransposons, sometimes known as “jumping genes.” These are segments of your own DNA that can cut and paste genetic material from one spot to another, and they become more active under stress. When this happens, the inserted viral fragments can be “read” back into RNA, which a PCR test then detects.
The researchers emphasized that none of the inserted fragments contained enough genetic information to produce a live virus. No infectious virus was recovered from patients who tested positive weeks or months after recovery. The test is simply picking up molecular echoes of an infection that’s already over.
When You’re Actually Contagious
The window of contagiousness is much shorter than the window of testing positive. Research on vaccinated individuals with mild or asymptomatic Omicron infections found that they shed infectious virus for 6 to 9 days after symptom onset or diagnosis, but not after day 10. A UK study found that the probability of recovering live, culturable virus from a sample drops to just 8% once the PCR cycle threshold value (a measure of how much viral material is present) rises above 35, and drops to 6% after 10 days from symptom onset.
In simple terms, the less virus in your sample, the less likely you are to be contagious. As your immune system wins the fight, the amount of detectable virus plummets, even if the ultra-sensitive PCR test can still find traces. This is why rapid antigen tests are more useful for gauging infectiousness: they go negative when viral levels drop below a meaningful threshold.
Factors That Extend Positive Tests
Several things can push your timeline longer in either direction. Symptomatic infections produce more virus and take longer to clear than asymptomatic ones. People with weakened immune systems face a significantly extended timeline. A systematic review of 183 immunocompromised patients found the median duration of detectable viral RNA was 56 days from the first positive test, with a range stretching from 21 days to over 400 days. Among those patients, people with blood cancers had the longest median detection at 72 days, while solid organ transplant recipients had the shortest at 41 days.
More concerning, some immunocompromised patients shed live, culturable virus (meaning they were potentially contagious) for a median of about 60 days, with the longest documented case reaching 268 days from the first positive test. This is vastly different from the general population, where contagiousness typically ends within 10 days.
Antiviral Rebound
If you took an antiviral medication during your infection, there’s a chance of testing positive again shortly after finishing treatment. A study of over 11,000 patients found that about 3.5% tested positive again within 2 to 8 days of completing their 5-day course, and about 5.4% tested positive within 30 days. Symptoms also rebounded in roughly 6% of patients over the same 30-day window. This rebound is generally mild and short-lived, but it can be confusing if you thought you were in the clear.
Which Test to Use and When
If you’re trying to figure out whether you’re still contagious, use a rapid antigen test. Two negative rapid tests taken 48 hours apart are a reasonable signal that your viral levels have dropped below the point of easy transmission. A PCR test taken during this same period could easily still read positive, but that result tells you very little about your ability to spread the virus to others.
If you get sick again within 90 days of a previous infection and want to know whether it’s a new infection, a rapid antigen test is again the better choice. A PCR test can’t reliably distinguish between leftover RNA from your first infection and a genuine reinfection during that window. That said, reinfection within 90 days is possible, so new symptoms shouldn’t be automatically dismissed as residual.