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BACKGROUND:Some COVID-19 cases test positive again for SARS-CoV-2 RNA following negative test results and discharge, raising questions about the meaning of virus detection. Better characterization of re-positive cases is urgently needed. METHODS:Clinical data were obtained through Guangdong's COVID-19 surveillance network. Neutralization antibody titre was determined using microneutralization assays. Potential infectivity of clinical samples was evaluated by cell inoculation. SARS-CoV-2 RNA was detected using three different RT-PCR kits and multiplex PCR with nanopore sequencing. FINDINGS:Among 619 discharged COVID-19 cases, 87 re-tested as SARS-CoV-2 positive in circumstances of social isolation. All re-positive cases had mild or moderate symptoms at initial diagnosis and were younger on average (median, 28). Re-positive cases (n = 59) exhibited similar neutralization antibodies (NAbs) titre distributions to other COVID-19 cases (n = 218) tested here. No infectious strain could be obtained by culture and no full-length viral genomes could be sequenced from re-positive cases. INTERPRETATION:Re-positive SARS-CoV-2 cases do not appear to be caused by active reinfection and were identified in ~14% of discharged cases. A robust NAb response and potential virus genome degradation were detected in almost all re-positive cases, suggesting a substantially lower transmission risk, especially through respiratory routes.

Original publication

DOI

10.1016/j.ebiom.2020.102960

Type

Journal article

Journal

EBioMedicine

Publication Date

24/08/2020

Volume

59

Addresses

Guangdong Provincial Institution of Public Health, Guangdong Provincial Center for Disease Control and Prevention, 160 Qunxian Rd, Dashi Town, Panyu District, Guangdong Province, Guangzhou 511430, China; Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China; School of Public Health, Southern Medical University, Guangzhou, China.