Your questions, answered "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 First, we are sorry to hear you experienced a breakthrough coronavirus infection. People who become infected with the coronavirus can actually test positive for quite a while, which may be happening to you, 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 to determine they are no longer contagious. In fact, 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 why some researchers are keener on antigen tests — the faster, sometimes less accurate tests that can be done at home. Nuzzo said the fact that these tests are less sensitive to smaller amounts of viral RNA that can be found in people who are no longer contagious, "may be a feature rather than a defect." Also, she said, antigen tests can be repeated to confirm any negative test results. All of that said, you should comply with testing and isolation guidelines from the Centers for Disease Control and Prevention. For testing, the CDC recommends that people who develop potential symptoms get tested. Beyond that, those who are vaccinated should be tested three to five days after exposure to someone with suspected or confirmed coronavirus infection. Unvaccinated people should be tested after potential exposure, too, as well as after engaging in higher-risk activities such as traveling or attending crowded gatherings. In terms of isolation, the CDC states that 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 such as acetaminophen. Those who test positive but do not have any symptoms should isolate for 10 days after their initial positive test result. The window in which people are most contagious is likely to be two or three days before and after symptoms appear, though scientists are still learning about this and other characteristics of the virus. Nuzzo said that based on what they know 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. | 
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