The first follow-up RT-PCR
As per national protocol, RT-PCR testing was not performed upon
discharge to confirm viral clearance. The first follow-up RT-PCR study
was performed 30 days after the first positive RT-PCR result in each
patient, which was after at least 14 days of being asymptomatic.
Considering the short interval between the onset of the disease and the
test, no recorded negative RT-PCR result at discharge, and the fact that
the patients who tested positive were asymptomatic, we believe that the
positive results show continued viral shedding rather than re-infection.
The four patients who tested positive were not significantly different
from others in terms of the severity of the initial illness, duration of
the first admission, age, or underlying conditions to suggest a risk
factor for a longer viral shedding period. Other studies have reported
that up to 14% of recovering asymptomatic patients who tested negative
upon discharge, re-test positive [29]. Other studies have reported
patients who became symptomatic after a short symptom-free period. A
24-year-old health-worker became symptomatic and tested positive for
SARS-CoV-2 within 52 days of an initial symptomatic diagnosis of
COVID-19. Similar to our study, no confirmatory RT-PCR testing was
performed at discharge. Serum antibodies were not detected at the
beginning of the second symptomatic period, which can represent an
incomplete immune response that left the infection temporarily dormant,
only to be re-activated again; and although the patient was symptomatic
and had occupational contact with infected patients during her
symptom-free period, re-activation was considered more probable than
re-infection [30]. Similar studies have reported a return of mild or
even severe symptoms; but within a short time frame and without genetic
analysis of the infective pathogens, they were reported to be cases of
reactivation rather than re-infection [31-34].