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Chiara DiGiallorenzo first started feeling sick on 6 March. She’d recently flown to Los Angeles to visit her boyfriend, and she hung out with a friend who was in town from London. Her friend wasn’t feeling well, but she figured he just had a 48-hour bug. Soon after, DiGiallorenzo and a few of her friends started to feel run down.
“We all had high fevers, terrible body aches and no sense of taste nor smell,” DiGiallorenzo, 25, told HuffPost. Her friends, all of whom are young and otherwise healthy, were able to beat the virus in a few days. But DiGiallorenzo, who has an underlying health condition, was still battling the sickness days later.
When she developed tightness in her chest, she decided to have a doctor check out her lungs and test her for Covid-19. A positive test came back two days later.
For 10 days, DiGiallorenzo had a fever. On 17 March, her symptoms cleared, and, according to the guidelines that state you are no longer contagious three days after your symptoms end, she was officially released from isolation.
But out of an abundance of caution, she got checked out one more time by her doctor. Even though she no longer had symptoms, she again tested positive for Covid-19 — 20 days after she experienced her first symptom.
“My doctors are pretty unclear as to what my positive test indicates. They explained that it could either be that I still actively have the virus, or it is the dead virus [and] particles shedding,” DiGiallorenzo said. “It’s somewhat of a guessing game.”
Exactly how long Covid-19 lingers and spreads is still somewhat of a mystery.
DiGiallorenzo is right to say it’s somewhat of a guessing game. Researchers don’t know why some people are testing positive for longer than others ― and they’re scrambling to figure out if those prolonged positive test results mean people are still contagious.
A recent study out of Beijing examined 16 patients with Covid-19 and found that half continued to test positive even after their symptoms, such as cough and fever, ended. Those patients had “markers of shedding,” indicating they could still spread the disease for up to eight days after they recovered.
Two other studies from Wuhan, China, found similar evidence, suggesting that people are still contagious after they’ve clinically recovered. On average, people with Covid-19 shed or emit the virus for 20 days, with some shedding it for up to 37 days.
One of the major obstacles that’s prevented us from gathering more evidence on how long the virus sheds is the ongoing lack of widespread testing. In the United States, we barely have enough tests to evaluate those who are presenting symptoms for the first time, let alone people who are coming back for a second test. DiGiallorenzo’s experience is rare.
“Because there is currently a shortage of tests, testing post-symptomatic people may not be a priority for their use,” said Ben Singer, a pulmonologist and assistant professor of pulmonary and critical care medicine at Northwestern University Feinberg School of Medicine.
Scientists have a few theories about why you can still test positive after you feel better.
Health experts have a few guesses as to why some people may test positive for days, even weeks after they recover.
The first is that the Covid-19 test is detecting remains and traces of the virus, but not the live, infectious virus itself. It’s been seen before that the remnants of the virus are detected but not the live, infectious virus, according to Singer.
“It’s possible that the immune system has destroyed the virus and you’re just seeing lingering pieces of its genetic material, and that’s what you’re detecting,” Singer said.
There is also the rare event where someone’s test produces a false positive, or a positive result when in actuality they don’t have the virus, according to Singer. False positives aren’t common, but they do occur from time to time, mainly due to a specimen mixup or accidental contamination in the lab.
Health experts also suspect prolonged positives may be linked to deficiencies in the immune system.
Take Mark Jorgenson, for example, who was aboard the Diamond Princess cruise ship mid-February when one of the first Covid-19 outbreaks outside of Wuhan struck. Upon returning to America, Jorgenson ― who takes immunosuppressant drugs after two kidney transplants ― tested positive for Covid-19 on 23 Feb.
Despite being at risk for Covid-19 complications, Jorgenson was symptom-free. Unlike his wife, Jerri, who also had Covid-19 but tested negative after a couple of weeks, Jorgenson continued to carry the virus. He was quarantined at his home in St. George, Utah, in late February, and the state health department tested him three times a week, but he kept testing positive. Even though he was supposed to show two negative tests before being cleared, the Utah Department of Health canceled further tests and declared him no longer a risk to the public in mid-March.
According to Singer, we see this play out in the immunocompromised with other respiratory infections, such as the flu or norovirus. Clearing the body of a virus is a tough job for any immune system, but those with weaker immune systems seem to have a harder time getting rid of it.
“People who are receiving immunosuppressant drugs for organ transplants or bone marrow transplants or even people with advanced HIV infection will often shed virus longer than someone who has an intact immune system,” said Dean Winslow, infectious diseases specialist at Stanford Health Care. In some cases, people can shed viruses for weeks, even months, after they feel well again.
It’s also not clear how this affects the length of time you’re contagious, so social distancing remains vital.
There’s a big gap in knowledge regarding if and how people shed viruses after recovering from the illness. Post-recovery shedding has been under-researched, not just with Covid-19 but other infections as well.
According to Winslow, people could, in theory, be less contagious after they’ve recovered than they were at the start or peak of their illness. It makes sense, given at the very least you’re not coughing or sneezing as much, therefore you’re not emitting respiratory droplets as easily.
But again, we don’t yet have data that proves anyone is less contagious at the end of the illness. “There’s really a lot that we don’t know,” Winslow said.
For the most part, the infection seems to vary from person to person. “People do shed the virus for a couple of days before they display symptoms and then there’s also a number of people that really never get that symptomatic and yet can still probably shed the virus for several days if not longer,” Winslow said.
This is exactly why social distancing and sheltering in place are so critical right now. The goal of these measures is to drastically “decrease the transmission from either minimally symptomatic or asymptomatic people,” Winslow added. We just don’t know who is spreading the virus and how much.
Given the rapid spread and infectivity of Covid-19, it may be wise to continue staying home for some time even after recovering from the disease if you know you had it.
“I think the prudent thing would be to self isolate for a while longer,” Winslow said.