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Your coronavirus questions, answered: Could you still test positive for covid-19 months after the infection?

“I just completed a bout with breakthrough (likely variant delta) coronavirus. When I tested two weeks after my isolation period with no symptoms, I was still testing positive. Am I contagious to others? How long will I continue to test positive?”

— Ola in Texas

People who get infected with the coronavirus can test positive for quite a while, but that does not mean they are still contagious to others. One expert said that although people who receive an initial positive test result should certainly assume they are infectious and act accordingly, they do not need a negative result after the recommended isolation period. Some people have continued to test positive for months after an infection with the coronavirus.

This is more likely to happen when using polymerase chain reaction (PCR) tests, which are the gold standard but are also very sensitive in detecting remnants of the coronavirus. The test is designed to look for evidence of viral RNA — the genetic material of the coronavirus — and the human body can shed viral RNA for a long time as it is getting rid of the virus, said Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security. But, she said, the test could be simply detecting fragments of RNA — not the whole, active virus, which would be required to infect other individuals.

“Just finding evidence that there’s viral RNA in your nose is not a great indication of whether you’re contagious,” she said.

There are other ways to try to assess whether the detected material is capable of transmission, such as taking a culture and trying to grow the virus in a lab. But, Nuzzo said, none of it is a perfect science.

That is why some researchers are keener on the faster, sometimes less accurate antigen tests that can be done at home. These tests are less sensitive to smaller amounts of viral RNA that can be found in people who are no longer contagious.

All of that said, you should comply with testing and isolation guidelines from the Centers for Disease Control and Prevention. The CDC recommends that people who develop potential symptoms get tested. Vaccinated people should be tested three to five days after exposure to someone with a suspected or confirmed coronavirus infection. Unvaccinated people should be tested after potential exposure, as well as after engaging in any higher risk activities.

In terms of isolation, the CDC says people who are symptomatic should isolate for 10 days after first experiencing symptoms and for 24 hours after they have been fever-free without using any fever-reducing medications. Those who test positive but do not have any symptoms should isolate for 10 days after their initial positive test result.

Based on what is known right now, once you have completed your isolation period, you can assume you are no longer spreading the virus, despite what your test results show.

— Lindsey Bever

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