People who test positive after recovering from coronavirus are not reinfected or contagious, says study
People who test positive again for the new coronavirus, despite having already recovered from Covid-19, are not being reinfected, nor can they infect others, according to researchers of a new study. The findings could have major implications for scientists and health experts globally as countries struggle with how to safely reopen their economies.
The team studied 285 patients who had survived Covid-19, but subsequently tested positive after multiple negative tests showed they had recovered. Scientists were unable to find evidence that the patients remained infectious.
In the study, researchers tried to isolate infectious coronaviruses from samples taken from 108 people who retested positive. But the samples did not have infectious virus particles, and tested negative, according to results published by Korea Centers for Disease Control and Prevention (KCDC), South Korea, implying that these people are not currently infected with SARS-CoV-2, the virus that causes Covid-19.
The finding indicates that the diagnostic tests could be picking up on the genetic material from non-infectious or dead viruses. A second positive test after a negative result may mean the virus is simply taking its time leaving the body and is no longer able to infect others, said experts.
The researchers also found that the group of patients who tested positive a second time for the coronavirus had not passed on the disease to others. The scientists found a total of 790 contacts, none of whom tested positive as a result of being exposed to the patients who re-tested positive. Based on the findings, experts say that the absence of infectious virus particles imply these people cannot transmit the novel coronavirus to others.
Further, when the scientists examined 23 of those patients for antibodies against the coronavirus, almost all had neutralizing antibodies that may stop the virus from getting into cells. “Based on active monitoring, epidemiological investigation and laboratory testing of re-positive cases and their contacts, no evidence was found that indicated the infectivity of re-positive cases.
Of the 447 re-positive cases as of May 15, an epidemiological investigation was conducted on 285 cases and laboratory analysis on 108 cases. From the monitoring of 790 contacts of the 285 re-positive cases, no case was found that was newly infected solely from contact with re-positive cases during the re-positive period,” says the study. “Virus isolation in cell culture of respiratory samples of 108 re-positive cases, all result was negative (that is, virus not isolated). Of the 23 re-positive cases from which the first and the second serum samples were obtained, 96% were positive for neutralizing antibodies.”
The study was conducted in response to reports of multiple cases testing positive for SARS-CoV-2 after being discharged from isolation in South Korea. While the research is preliminary, and similar investigations are being done, the KCDC has stopped applying the previous protocols for the management of confirmed cases after discharge from isolation and for the management of re-positive cases. Under the new protocols, no additional tests are required for cases that have been discharged from isolation.
Effective from May 19, management of confirmed cases after discharge from isolation and management of re-positive cases will no longer be conducted. “Reporting and investigation of re-positive cases and investigation of contacts of re-positive cases will be continued as before for the purposes of research and investigation. However, based on experts’ recommendations, the terminology for referring to such cases will be changed from “re-positive” to “PCR re-detected after discharge from isolation,” say health officials.
According to the US CDC, the onset and duration of viral shedding and the period of infectiousness for Covid-19 are not yet known. “It is possible that SARS-CoV-2 RNA may be detectable in the upper or lower respiratory tract for weeks after illness onset, similar to infections with MERS-CoV and SARS-CoV. However, detection of viral RNA does not necessarily mean that infectious virus is present,” say experts.