Re-positive discharged COVID-19 patients are at low transmission risk for SARS-CoV-2 infection– a finding from recovered COVID-19 patients in Wuhan, China (preprint)

ABSTRACT

Discharged COVID-19 patients have been found to be retested positive for SARS-CoV-2 (re-positive), which has widely raised concern among the public. We investigated the prevalence and transmission risk of re-positive cases in discharged COVID-19 patients and their SARS-CoV-2-specific antibody levels in Wuhan, China. Of 1065 discharged COVID-19 patients investigated, 518 (48.64%) patients were males; the mean age was 53.29 ± 14.91 years, with a median duration of 40 (IQR 31–47) days since discharge. 63 patients were tested re-positive for SARS-CoV-2, with the re-positive prevalence to be 5.92% (95%CI 4.50%-7.33%). The re-positive prevalence was higher in females (7.86%, 95%CI 5.61%-10.12%) than that in males (3.86%, 95%CI 2.20%-5.52%, P = 0.006). Re-positive prevalence was similar in patients tested positive and negative for IgG (6.01% vs 5.56%, P = 0.821) or IgM (6.38% vs 5.07%, P = 0.394). Illness severity and duration from illness onset to retest were not associated with the risk of positive results for SARS-CoV-2 after discharge. All 196 environmental samples collected from 49 re-positive patients were tested negative for SAR-CoV-2. Only one close contact to the re-positive patient had been tested positive for SARS-CoV-2; however, he might be a previous COVID-19 case but had not been detected before. Viral culture of 6 nasopharyngeal specimens presented no cytopathic effect of Vero E6 cells. Virus sequencing of 11 nasopharyngeal specimens indicated genomic fragments of SARS-CoV-2. 898 (84.72%) patients and 705 (66.51%) patients were tested positive for SARS-CoV-2-specific IgG and IgM, respectively. Self-report symptoms at the survey were similar, regardless of the level of antibody. All the re-positive patients and their matched non-re-positive patients were tested negative for SARS-CoV-2 four months later. These findings indicate that Testing re-positive of SARS-CoV-2 is common in discharged COVID-19 patients, but no evidence showed the transmission risk of these re-positive cases. Further isolation of recovered COVID-19 patients is unnecessary. However, only 85% recovered COVID-19 patients had SARS-CoV-2-specific antibody, which suggested discharged COVID-19 patients still had potential re-infection risk.