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Low infectious risk of re-positive COVID-19 patients: a single-center study
Lijun Liang1, Qianfang Guo1, Huan Zhang1
1Guangdong Provincial Center for Disease Control and Prevention, Guangdong Workstation for Emerging Infectious Disease Control and Prevention, Chinese Academy of Medical Sciences, No. 160, Qunxian Road, Dashi Town, Panyu District, Guangzhou 511430, Guangdong, China.
Objective:
The aim of this study was to investigate the infectiousness of re-positive coronavirus disease 2019 (COVID-19) patients.
Methods:
All nucleic acid testing (NAT) was performed using throat swabs, nasopharyngeal swabs, and anal swabs, which were tested by Fluorescent quantitative realtime PCR. Re-positive cases were defined as a discharged patient who re-tested positive by NAT. Micro-neutralization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was performed based on the methods for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) viruses. IgM and IgG against the N protein of SARS-CoV-2 were determined by ELISA.
Results:
A total 255 (16.04%) of 1590 COVID-19 patients were re-positive. The re-positive cases were more likely to occur in patients in the 20-39 years age group and in patients with disease of moderate severity. Quantitative PCR showed that cycle threshold (Ct) values and viral loads were both far lower than in the hospitalized COVID-19 patients. The viral load in re-positive cases was very low. Viral culture of the samples from re-positive patients showed no cytopathic effect, and NAT of the culture medium of viral cultures all exhibited negative results.
Conclusion:
The viral load in re-positive cases was very low; patients were not infectious and the risk of human-to-human transmission was extremely low. Discharged COVID-19 patients should undergo home health management for 3 weeks.
