When Testing Positive For The Coronavirus Doesn’t Mean You’re Contagious

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The extended isolation period gave Amanda Joyce and her husband Patrick some extra time to set up the room for a baby girl she's expecting in early August. (Jesse Costa/WBUR)
The extended isolation period gave Amanda Joyce and her husband Patrick some extra time to set up the room for a baby girl she's expecting in early August. (Jesse Costa/WBUR)

Amanda Joyce barely noticed the tickle in her throat and the little dry cough that started on March 19th. She only realized the significance two days later, when she woke up with a fever and body aches. Joyce had COVID-19.

“It was like someone had done WrestleMania and just totally took me down,” says Joyce who is now 31 weeks pregnant.

The virus slammed Joyce for at least a month. By late April, she was feeling better and figured the virus must be gone. To return to work, as a labor and delivery nurse at Newton Wellesley Hospital, Joyce would need two negative diagnostic tests, a day apart. So Joyce got tested, at least a dozen times, but every time she’d get a negative, the next test would come back positive. Joyce, her husband and young son stayed home, in isolation, assuming she was still contagious.

“I was just cautious,” she says. “I was still getting those positive tests. No one could tell what it actually meant.”

That’s because research that would reveal how long someone with the coronavirus remains contagious emerged while Joyce was sick. The answer varies, from five days after the start of symptoms to 11 days. The findings are based on just a handful of studies and a small sample of patients. But the results are shifting the way doctors, public health leaders and some policymakers think about whether a positive diagnostic test result means someone can still spread the infection.

Joyce finally received that definitive second negative test in late May, almost 10 weeks after she noticed a tickle in her throat.  As it turns out, her employer, Mass General Brigham, has decided to scrap that requirement, one of two ways the CDC says health care workers can be cleared to return to their jobs.

Instead, Mass General Brigham will use a more conservative version of the CDC’s other “cleared to work” option: an employee who has tested positive can return to work 14 days after their first symptom, if their symptoms are gone and they have no fever. Managing a fever with meds doesn’t count.

“Based on all of the studies, we decided that it made much more sense to move to this time and symptom-based criteria,” says Dr. Erica Shenoy, associate chief of infection control at Massachusetts General Hospital.

Only about 5% of patients with COVID-19 continue to test positive for more than a month, as did Joyce. But a study published this week out of Singapore found that 70% are still positive 15 days after the first sign of COVID-19. That means more than a million U.S. residents who’ve had the coronavirus might still test positive beyond the period when research shows they can infect others.


More health systems and government agencies are moving away from the two negative test requirement to 10 days in isolation and a symptom assessment. That’s true for the contact tracing project in Massachusetts and for the isolation sites created for people who are homeless in the state. Dr. Josh Barocas, who’s been advising the homeless COVID-19 response, says his thinking has shifted away from testing in just the last week or two as more research about the shorter period of contagion came out.

It is truly amazing how fast things change,” says Barocas, an infectious disease specialist at Boston Medical Center. “While I think this is a reasonable approach right now, if new data emerge next week or the week after then we are going to have to, all or us, retool our approach.”

This question of whether a positive test means someone is still contagious is becoming very difficult for some hospitals. Dr. Richard Ellison, the hospital epidemiologist at UMass Memorial Medical Center, says It’s hard to know what precautions to take when patients who appear to have recovered from COVID-19 come back with complications or for surgery or because they’ve had an accident.

“Do hospitals say we have to treat this person the same way we treat someone who is very sick with COVID right now?” he asks. “We’ve got limited supplies of gowns and gloves and masks. Do we want to use these taking care of some unnecessarily?”

Ellison says patients who continue to test positive but are ready for discharge are a challenge for hospitals as well. He’s encountering patients who live in nursing homes or assisted living apartments who can’t go home because their facility requires two negative tests. Ellison says we need results that show a low positive or high positive, for example, or that tell someone whether the virus is active or dead. Those tests aren’t available yet.

“Right now we’re getting a black and white answer,” he says. “The test is positive or it’s negative, but we’re not getting variation in that.”

But why does a nasal swab still find signs of the coronavirus weeks or months after Joyce and some patients have recovered? As Shenoy explains, the test looks for genetic material that signals the presence of the virus.

“It doesn’t tell you if it’s alive,” she says. “So just because you identify virus through this test does not mean that the person is infectious and capable of spreading disease to others.”

The growing body of research that shows a positive test result does not mean someone is contagious may be difficult for employers, school administrators and summer camp directors who have suggested using diagnostic tests to decide who is safe to be near and who isn’t.

Ellison says mass testing may lead to a lot of unnecessary tests and headaches.

“Some kids might spend the entire summer getting tested, before they’d be able to be approved for going to camp,” he says.

Shenoy recommends the 10-day isolation rule for those who’ve had symptoms. Barocas says testing, tracking symptoms, social distancing and heavy cleaning will all be needed. Some testing will be needed to find employees or students or campers who have the coronavirus but do not show symptoms. Again, a positive test doesn’t mean that person is contagious. The guidelines say they should still isolate for 10 days, although a study out this week finds that people who are asymptomatic spread the virus for only eight days.

Joyce is thrilled to be out from under the COVID-19 microscope, although she is still participating in a long term study of the coronavirus impact on pregnancy, childbirth and the postpartum experience. She’s been visiting with friends and family, from a safe distance, after two and half months of nothing but virtual contact.

“This weekend, when I finally got the go-ahead and was cleared, is the first time I haven’t felt like a lab experiment,” she laughs. “It’s kind of a nice feeling to be let back into human society, let out of the cage.”

Joyce plans to be back at work next week but won’t be on the job for long. She’s now 31 weeks pregnant.

This segment aired on May 29, 2020.

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Martha Bebinger Reporter
Martha Bebinger covers health care and other general assignments for WBUR.



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