“Researchers are finding evidence that patients
who test positive for the coronavirus after recovering aren’t capable of
transmitting the infection, and could have the antibodies that prevent them
from falling sick again.
“Scientists from the Korean Centers for Disease
Control and Prevention studied 285 Covid-19 survivors who had tested positive
for the coronavirus after their illness had apparently resolved, as indicated
by a previous negative test result. The so-called re-positive patients weren’t
found to have spread any lingering infection, and virus samples collected from
them couldn’t be grown in culture, indicating the patients were shedding
non-infectious or dead virus particles.
“The
findings, reported late Monday [May 18], are a positive sign for regions looking
to open up as more patients recover from the pandemic that has sickened at
least 4.8 million people. The emerging evidence from South Korea suggests those
who have recovered from Covid-19 present no risk of spreading the coronavirus
when physical distancing measures are relaxed.
“The results mean health authorities in South
Korea will no longer consider people infectious after recovering from the
illness. Research last month showed that so-called PCR tests for the
coronavirus’s nucleic acid can’t distinguish between dead and viable virus
particles, potentially giving the wrong impression that someone who tests
positive for the virus remains infectious.
“The
research may also aid in the debate over
antibody tests, which look for markers in the blood that indicate exposure to
the novel coronavirus. Experts believe antibodies probably convey some level of
protection against the virus, but they don’t have any solid proof yet. Nor do
they know how long any immunity may last.
“A recent study in
Singapore showed that recovered patients from severe acute respiratory
syndrome, or SARS, are found to have ‘significant levels of neutralizing
antibodies’ nine to 17 years after initial infection, according to researchers
including Danielle E. Anderson of Duke-NUS Medical School.
“Other scientists have found higher
levels of IgM, an antibody that appears in response to exposure to an antigen,
in children, according to an article published on medRxiv. That suggests younger
populations have the potential to produce a more potent defense against
Covid-19. The study has not been certified by peer review.
“As a result of the findings in the
South Korea study, authorities said that under revised protocols, people should
no longer be required to test negative for the virus before returning to work
or school after they have recovered from their illness and completed their
period of isolation. ‘Under
the new protocols, no additional tests are required for cases that have been
discharged from isolation,’ the Korean CDC said in a report. The agency said it
will now refer to ‘re-positive’ cases as ‘PCR re-detected after discharge from
isolation.’
“Some coronavirus patients have tested positive again for the
virus up to 82
days after becoming infected. Almost all of the cases for which blood tests
were taken had antibodies against the virus” (Bloomberg,“Covid Patients Testing Positive After Recovery Aren’t Infectious, Study Shows” by Heesu Lee and Jason Gale with
assistance by Peter Pae and Claire Che).
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