Re-detectable positive SARS-CoV-2 RNA tests in patients who recovered from COVID-19 with intestinal infection
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Protein & Cell
LETTER
Dear Editor, Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2), a novel coronavirus that causes Coronavirus Disease 2019 (COVID-19) (Yang and Wang, 2020), has spread to more than 200 countries and infected more than 9,000,000 people as of Jun 2020. Tens of thousands of patients with COVID-19 have recovered and been discharged from hospital. However, there are reports of recovered patients who subsequently tested positive for SARSCoV-2 after discharge (re-detectable positive, RP) (An et al., 2020; Lan et al., 2020), and this has led to increasing focus on the mechanism(s) underlying RP. Several studies of discharged patients have been performed to investigate the proportion of RP and the clinical symptoms of these patients (An et al., 2020; Lan et al., 2020). One study revealed that four patients had positive SARS-CoV-2 RT-PCR tests 5 to 13 days after discharge (Lan et al., 2020), while a retrospective study in Wuhan, China reported that 8/108 (7.4%) patients were RP (Cao et al., 2020). Moreover, 14.5% of convalescent patients (n = 38) were RP for SARS-CoV-2 RNA in RT-PCR tests of both anal and nasopharyngeal swabs (An et al., 2020). RP is usually observed in young patients who had mild or moderate COVID-19 symptoms on the first admission, and several significant characteristic features including early RNAnegative conversion, fewer comorbidities, and more frequent upper respiratory symptoms (An et al., 2020). No obvious clinical symptoms were reported on the second admission of these patients (An et al., 2020; Lan et al., 2020; Cao et al., 2020). In recent reports, close contacts of RP patients were tested negative for SARS-CoV-2 RNA (An et al., 2020; Lan et al., 2020). However, as the patients were usually in quarantine after discharge, the infectivity of the patients might be underestimated. Two patients who were RP continued to be positive for SARS-COV-2 RNA for more than 90 days (Cao et al., 2020). Careful consideration should therefore be given to the potential for patients who are RP to become chronic virus-carriers. The cause of RP remains controversial, and consequently it is difficult to set standards for discharge and follow-up of
© The Author(s) 2020
patients. False negatives in qRT-PCR tests may partially explain the RP in some cases, because the lower limit of detection (LOD) of commercial RT-PCR kits is relatively high (An et al., 2020). The residual viremia could be another factor that leads to RP. Pathological examination of a readyfor-discharge patient who had COVID-19 identified viral particles in the pneumocytes. Several studies have reported the presence of SARS-CoV-2 RNA and viral particles in the gastrointestinal tracts of patients who had COVID-19, and that fecal samples remained viral RNA-positive after patients were respiratory-negative for SARS-CoV-2 and were discharged from hospital (Xu et al., 2020), thus highlighting the prolonged presence of SARS-CoV-2 in the gastrointestinal tract. Here, we investigated whether the intestine might be a “reservoir” of SAR
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