For reasons unknown, about one in six people who recovered from COVID-19 subsequently retested positive at least 2 weeks later, researchers reported in a study in Italy.
Sore throat and rhinitis were the only symptoms associated with a positive result. “Patients who continued to have respiratory symptoms, especially, were more likely to have a new positive test result,” lead author Francesco Landi, MD, PhD, said in an interview.
“This suggests the persistence of respiratory symptoms should not be underestimated and should be adequately assessed in all patients considered recovered from COVID-19,” he said.
“The study results are interesting,” Akiko Iwasaki, PhD, an immunobiologist at Yale University and the Howard Hughes Medical Institute, both in New Haven, Conn.,, said in an interview. “There are other reports of RNA detection postdischarge, but this study … found that only two symptoms out of many – sore throat and rhinitis – were higher in those with PCR [polymerase chain reaction]-positive status.”
The study was published online Sept. 18 in the American Journal of Preventive Medicine.
The findings could carry important implications for people who continue to be symptomatic. “It is reasonable to be cautious and avoid close contact with others, wear a face mask, and possibly undergo an additional nasopharyngeal swab,” said Dr. Landi, associate professor of internal medicine at Catholic University of the Sacred Heart in Rome.
“One of most interesting findings is that persistent symptoms do not correlate with PCR positivity, suggesting that symptoms are in many cases not due to ongoing viral replication,” Jonathan Karn, PhD, professor and chair of the department of molecular biology and microbiology at Case Western Reserve University, Cleveland, said in an interview.
“The key technical problem, which they have discussed, is that a viral RNA signal in the PCR assay does not necessarily mean that infectious virus is present,” Dr. Karn said. He added that new comprehensive viral RNA analyses would be needed to answer this question.
Official COVID-19 recovery
To identify risk factors and COVID-19 survivors more likely to retest positive, Dr. Landi and members of the Gemelli Against COVID-19 Post-Acute Care Study Group evaluated 131 people after hospital discharge.
All participants met World Health Organization criteria for release from isolation, including two negative test results at least 24 hours apart, and were studied between April 21 and May 21. Mean age was 56 and 39% were women. Only a slightly higher mean body mass index of 27.6 kg/m2 in the positive group versus 25.9 in the negative group, was significant.
Although 51% of survivors reported fatigue, 44% had dyspnea, and 17% were coughing, the rates did not differ significantly between groups. In contrast, 18% of positive survivors and 4% of negative survivors had a sore throat (P = .04), and 27% versus 12%, respectively, reported rhinitis (P = .05).
People returned for follow-up visits a mean 17 days after the second negative swab test.
Asymptomatic COVID-19 carriers
“These findings indicate that a noteworthy rate of recovered patients with COVID-19 could still be asymptomatic carriers of the virus,” the researchers noted in the paper. “Even in the absence of specific guidelines, the 22 patients who tested positive for COVID-19 again were suggested to quarantine for a second time.”
No family member or close contact of the positive survivors reported SARS-CoV-2 infection. All patients continued to wear masks and observe social distancing recommendations, which makes it “very difficult to affirm whether these patients were really contagious,” the researchers noted.
Evaluating all COVID-19 survivors to identify any who retest positive “will be a crucial contribution to a better understanding of both the natural history of COVID-19 as well as the public health implications of viral shedding,” the authors wrote.
One study limitation is that the reverse transcriptase–PCR test reveals genetic sequences specific to COVID-19. “It is important to underline that this is not a viral culture and cannot determine whether the virus is viable and transmissible,” the researchers noted.
“In this respect, we are trying to better understand if the persistence of long-time positive [reverse transcriptase]–PCR test for COVID-19 is really correlated to a potential contagiousness,” they added.
Dr. Landi and colleagues said their findings should be considered preliminary, and larger data samples are warranted to validate the results.
Dr. Landi and Dr. Karn disclosed no relevant financial relationships. Dr. Iwasaki disclosed a research grant from Condair, a 5% or greater equity interest in RIGImmune, and income of $250 or more from PureTec.
A version of this article originally appeared on.