The Surprising Reason Behind the Most Recent Major CDC Guideline Change

You may find yourself self-isolating for less time because of the CDC's new perspective on testing.

At this point in the pandemic, medical experts agree that getting COVID testing done quickly is vital to being able to keep outbreaks at bay. Test results help doctors and officials spot new cases and isolate patients before they can spread the disease. That's why the Centers for Disease Control and Prevention (CDC) had recommended that anyone who tested positive for COVID-19 should self-isolate until they eventually test negative for the virus not once, but two times. But recently, the CDC announced that patients can now instead end their isolation 10 days after they first show symptoms, without needing negative test results. So, what's the reasoning behind the CDC isolation guideline change? Well, it all comes down to the details of the testing process, says John Brooks, MD, Chief Medical Officer of the CDC's COVID-19 response.

The most common COVID tests are polymerase chain reaction (PCR) tests. The PCR test is "typically highly accurate," according to the Food and Drug Administration (FDA), but it's also highly sensitive, meaning a test could still come back positive for someone who had been sick but then recovered.

On a recent press call, Brooks said that "most people stop shedding live virus after 10 days," meaning they're no longer infectious. However, Brooks said, "they can keep shedding dead parts of the virus that that PCR test can discover."

a white woman wearing a face mask stares out the window

Brooks explained that while this sensitivity leads to an effective test in the early stages of the illness before people realize they're sick, it can actually have unintended consequences for people who already know they have COVID-19.

"It's led to people being kept out of work [or] kept in their house when they don't need to be," Brooks noted. As a result, he said, "We've stopped recommending PCR test for diagnosis once you've recovered."

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Another reason behind the CDC's isolation guideline change is the agency's increased understanding of the timeframe during which COVID-19 patients are most contagious. According to a recent report released by the CDC, about half of all coronavirus cases are spread during the pre-symptomatic stage, i.e. before a patient's symptoms develop. And while some recovered patients can still "shed detectable SARS-CoV-2 RNA in upper respiratory specimens" for up to three months, the CDC notes, the concentration of virus is so low that it makes transmission of the disease "unlikely." And for more CDC guidelines, check out 50 Essential COVID Safety Tips the CDC Wants You to Know.

Sarah Crow contributed reporting to this article.

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Zachary Mack
Zach is a freelance writer specializing in beer, wine, food, spirits, and travel. He is based in Manhattan. Read more
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