People Who Test Positive for COVID-19 After Recovering Aren't Infectious
By Julia Ries
Around the world, there have been several cases of people recovering from COVID-19 only to later test positive again and appear to have another infection.
Such cases have had doctors and researchers puzzling over whether recovered people continue to be contagious, and if they could get a second infection.
Now, new research published by the Korea Centers for Disease Control and Prevention has found that recovered COVID-19 patients who test positive again aren't infectious.
The study also found that most patients who recover have neutralizing antibodies — the type of antibody that confers immunity and protects people from getting sick again.
"This study addresses the question of whether patients who have recovered from COVID-19 are still infectious, and which is a question that has been troubling us for some time," said Dr. Heidi J. Zapata, a Yale Medicine infectious disease doctor. "This study suggests that patients that are recovered are no longer contagious."
The Viral Material in Re-Positive Cases Isn’t Infectious
The Korean study examined 285 patients who tested positive again for the new coronavirus after they recovered from COVID-19, which had been confirmed via a negative test result.
The researchers swabbed the patients and examined the viral material to determine whether it was still actively infectious.
The team was unable to isolate live viral material, indicating that the positive diagnostic tests were picking up dead virus particles.
"[This] may speak for the fact that the virus may be dead or not be fit enough to grow — therefore the virus may not be fit enough to infect a new host," said Dr. Andres Romero, an infectious disease specialist at Providence Saint John's Health Center in Santa Monica, California.
The researchers also tested 790 people who'd been in close contact with the "re-positive" patients. Of the 27 who tested positive, no cases appeared to be caused from exposure to someone who appeared to have a reinfection.
The report also found that the vast majority of recovered patients (96 percent) had neutralizing antibodies, indicating that they conferred immunity.
"Whether this is indicative of a completely protective response remains to be proven. If this study holds true, then people who have recovered can get back to work," Zapata said.
In response to the new findings, South Korea eliminated a policy requiring discharged patients to isolate for 2 weeks.
Conducting and Interpreting PCR Tests
The tests widely used to diagnose COVID-19 are called polymerase chain reaction (PCR) tests.
The tests swab a person's nose or throat and try to pick up the virus's genetic material, or RNA.
According to guidance from the U.S. Centers for Disease Control and Prevention (CDC), a positive result on a PCR test doesn't "necessarily mean infectious virus is present or that the patient is contagious."
Infectious disease experts have suspected that the test kits aren't picking up actively infectious viral material in recovered patients who test positive again, but rather dead remnants of the virus.
We see this occur with other viruses, too.
"We know other viruses like parainfluenza, human metapneumovirus, or RSV [respiratory syncytial virus] may linger for months in certain patients, and that does not represent infectious state," Romero said. "Coronavirus may be the same."
We Still Need to Practice Caution
While the findings are promising, infectious disease experts say we still need to practice caution.
More research is needed to validate these findings and determine whether they apply to distinct parts of the population, such as those who are immunocompromised.
It's common for immunocompromised patients — such as those with cancer — to continue testing positive for a virus for longer, since it takes their immune system more time to clear the virus out of their body.
"I don't think we can be 100 percent certain of whether each recovered person is no longer contagious. Again, this may differ with distinct population groups," Zapata said.
Physicians are seeing some hospitalized patients testing positive for a month after they were first swabbed for COVID-19. It's unclear whether these patients still shed infectious virus, according to Zapata.
Everyone's body mounts a distinct immune response based on their age and overall health. Different individuals will clear the virus out at different speeds, according to Zapata.
Until we have more data and a preventive vaccine, it's crucial to continue adhering to the safety precautions laid out by the CDC.
"The reality is that moving forward, the best approach will be keeping social/physical distancing, wearing a mask, and frequent hand hygiene in order to control the spread of the virus," Romero said.
The Bottom Line
Doctors and researchers have been unsure whether people who recover from COVID-19 who test positive again continue to be contagious, or if they could get a second infection.
New research published by the Korea Centers for Disease Control and Prevention has found that recovered COVID-19 patients who test positive again aren't infectious.
The study also found that most patients who recover have neutralizing antibodies that protect them from getting sick again.
Though the study is promising, health experts say we need more data to validate the findings and determine whether they apply to all patient populations.
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