Experts say the test you’re using might have an impact.
For most people, a positive COVID-19 test will happen early on in their infection—it’ll tip them off when to begin their isolation period, and, depending on symptoms, when they can enter back into the world. But for some people, a positive COVID-19 test may linger for weeks (or months) even after recovery—and the guidance for what to do with longstanding positive results is less clear.
The Centers for Disease Control and Prevention (CDC) currently provides guidance on what to do in the 10 days following a positive COVID-19 test: Those who didn’t develop symptoms can end isolation five days after a positive test; people who did develop symptoms can also end isolation after five days as long as symptoms are improving and they’ve been fever-free for 24 hours. Once out of isolation, people should continue to mask until day 10.
But according to the CDC, people can continue to test positive for COVID-19 for up to three months after their initial infection—so how does that play into the isolation recommendations? And does a lingering positive test mean you’re still contagious? Here’s what you need to know.
How Long Do People Usually Test Positive for COVID-19?
For the most part, people will test positive for COVID-19 on an antigen or rapid test for up to about 10 days, Matt Binnicker, PhD, director of clinical virology at the Mayo Clinic, told Health. But when using polymerase chain reaction (PCR) tests, people can test positive for even longer—up to two months, said Binnicker.
The CDC backs this up: In August 2020, the agency updated its isolation guidance to clarify that people can continue to test positive for COVID-19 up to three months after their initial diagnosis, but aren’t infectious to others in that time period.
The discrepancies between tests and the lengths of their positive results boils down to what each test looks for, and its sensitivity. PCR tests, for example, are designed to pick up viral RNA, or the virus’ genetic material, David Dowdy, MD, an epidemiologist with the Johns Hopkins Bloomberg School of Public Health, told Health. “Even if the virus is dead, the RNA can still be hanging around, so you can get a false positive [PCR test result] up to two months or so after the infection,” Dr. Dowdy said. “It’s not super super common, but it certainly does happen.”
Meanwhile, antigen tests—more often known as rapid or at-home tests—detect antigens, or specific proteins from the virus. The CDC says antigen tests are generally less sensitive than PCR tests, and both tests work best in symptomatic people.
According to the CDC, most people who continue to test positive for COVID-19 even after they’ve recovered from the virus don’t necessarily have to worry about passing the virus to others—but people who have a weakened immune system or suffered a particularly severe bout of COVID-19 and continue to test positive might.
“In some people…especially those with a compromised immune system, they may continue to be contagious for a longer period of time, especially if they continue to have symptoms,” said Binnicker. That’s because, according to Dr. Dowdy, their “immune system is not getting rid of the virus” as effectively as it should—which would also result in testing positive for COVID-19 for a longer period of time than usual.
The CDC recognizes this, too: The agency recommends extending the COVID-19 isolation period to up to 20 days for people who are severely immunocompromised or who were severely ill with COVID-19. A viral test may also be recommended for those people to determine if they’re able to be around others without the risk of spreading the virus.
What Should You Do if You Continue to Test Positive After You’ve Recovered?
If you test positive once for COVID-19, “in general, I would recommend not testing again,” said Dr. Dowdy. There’s an exception to that recommendation, according to the CDC, which says that if a person has access to an at-home test at the end of their five-day isolation period they can take it. If the test is positive, they should continue to isolate another five days. People who are immunocompromised or had severe COVID-19 may also test at the end of their isolation period.
According to Dr. Dowdy, if you were sick with COVID-19, then recovered, then begin having symptoms again, that would be the time for another rapid test. “But you just always have to be aware of the possibility of a false positive.”
Antigen tests are the way to go if you do have to test again for COVID-19 within three months of a previous COVID-19 test. “Because of the chance of persistent positive results by a molecular test, infected individuals should not use a [PCR] to determine if they are no longer infectious,” Binnicker said. The CDC also does not recommend retesting—presumably with a PCR test—within three months of a previous positive test.
For travelers who may need a negative test result to travel, the CDC advises people keep their positive test along with a doctor’s note that states you have been cleared to travel according to the CDC’s travel guidance—together, these act as “documentation of recovery.” However, according to Dr. Dowdy, simply being up to date on your COVID-19 vaccines can supersede the need for a negative test result in some instances.