Low infectious risk of re-positive COVID-19 patients: a single-center study

Liang, Lijun; Guo, Qianfang; Zhang, Huan; Lin, Shujian; Zheng, Huanyin; Li, Bosheng; Zhang, Yunqiang; Yu, Jianxiang; Zhou, Huiqiong; Liang, Yiwen; Huang, Xinxin; Wu, Jie

OBJECTIVE: This study aimed to investigate the infectiousness of re-positive COVID-19 patients. METHODS: All nucleic acid testing (NAT) was performed using throat swab, nasopharyngeal swab and anal swab were tested by real-time PCR. Re-positives were defined as a discharged patient re-tested positive in NAT. Micro-neutralization of SARS-CoV-2 was performed based on the methods of SARS and MERS viruses. IgM and IgG against N protein of SARS-CoV-2 were determined by ELISA assay. RESULTS: A total 255 (16.04%) out of 1590 COVID-19 cases were re-positive. The re-positives were more likely to occur in patients at the age of 20-39 and patients with moderate-severity. Quantitative PCR showed CT value and viral loads were both far lower than the hospitalized COVID-19 patients. The viral culture of the sample from re-positive cases showed no cytopathic effect, and NAT for the culture medium of viral culture all exhibited negative results. CONCLUSION: The viral load of the re-positive cases was very low, not infectious, and the risk of human-to-human transmission was extremely low. The discharged COVID-19 cases should undergo home health management for 3 weeks.