Abstract
Background: The coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a major global public health issue. SARS-CoV-2 infection is confirmed by the detection of viral RNA using reverse transcription polymerase chain reaction (RT-PCR). Prolonged viral shedding has been reported in patients with SARS-CoV-2 infection, but the presence of viral RNA does not always correlate with infectivity. Therefore, the present study aimed to confirm the presence of viable virus in asymptomatic or mildly symptomatic patients in the later phase of the disease, more than two weeks after diagnosis. Method: Asymptomatic or mildly symptomatic COVID-19 patients who had been diagnosed with the disease at least two weeks previously and admitted to a community treatment center (CTC) from 15 March to 10 April 2020 were enrolled in this study. Nasopharyngeal and salivary swab specimens were collected from each patient. Using these specimens, RT-PCR assay and viral culture were performed. Result: In total, 48 patients were enrolled in this study. There were no significant differences in baseline characteristics between the asymptomatic and mildly symptomatic patient groups. RT-PCR assay and viral culture of SARS-CoV-2 were performed using nasopharyngeal and salivary swabs. The results of RT-PCR performed using salivary swab specimens, in terms of cycle threshold (Ct) values, were similar to those of RT-PCR using nasopharyngeal swab specimens. In addition, no viable virus could be cultured from swab specimens collected from the late-phase COVID-19 patients with prolonged viral RNA shedding. Conclusions: In conclusion, our study suggests that even if viral shedding is sustained in asymptomatic or mildly symptomatic patients with later phase of COVID-19, it can be expected that the transmission risk of the virus is low. In addition, saliva can be used as a reliable specimen for the diagnosis of SARS-CoV-2 infection.
Highlights
The coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a major global public health issue
For the proper management of COVID-19 patients, asymptomatic or mildly symptomatic patients were admitted to community treatment centers (CTCs), which are non-medical facilities for isolation and monitoring
We attempted to confirm the presence of viable virus by performing reverse transcription polymerase chain reaction (RT-PCR) assay and culture using salivary and nasopharyngeal swabs of asymptomatic or mildly symptomatic COVID-19 patients who had been diagnosed with the disease and admitted to a CTC at least two weeks previously
Summary
The coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a major global public health issue. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis of respiratory specimens is the gold standard test for detecting SARS-CoV-2 infection [3]. Over the course of infection, viral RNA has been identified in respiratory tract specimens 1–3 days prior to the onset of symptoms. Prolonged viral shedding has been reported from nasopharyngeal swabs up to 63 days after the onset of symptoms among adult patients [7,8]. We attempted to confirm the presence of viable virus by performing RT-PCR assay and culture using salivary and nasopharyngeal swabs of asymptomatic or mildly symptomatic COVID-19 patients who had been diagnosed with the disease and admitted to a CTC at least two weeks previously
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