Isolation and identification of a severe acute respiratory syndrome coronavirus 2 strain in feces from COVID-19 patients in Shanghai

Objective To isolate and study the biological characteristics of severe acute respiratory syndrome coronavirus 2 （SARS-CoV-2） from feces of coronavirus disease 2019 （COVID-19） patients.

Methods Vero E6 cells were used for virus isolation and the isolated strains were tested by nucleic acid test， immunofluorescence test， virulence test and whole genome sequencing. 50% tissue culture infective dose （TCID₅₀） was calculated after the cell cultures of each generation were collected

Results Eight fecal specimens were inoculated with Vero E6 cells after treatment and cultured for 48 h. One specimen showed obvious cytopathic effect on Vero E6 cells. One SARS-CoV-2 out of 8 fecal samples from COVID-19 patients were isolated， and separation rate was 12.5%. The TCID₅₀ of P1， P2 and P3 were 10^4.0/0.2 mL， 10^4.5/0.2 mL and 10^4.75/0.2 mL， respectively. Only one of the 8 stool samples had SARS-CoV-2 virus replication and amplification， and the Ct value of the nucleic acid detection was about 10. The sequence of the isolation was more than 99.99% homologous with that of Wuhan-Hu-1（GenBank MN908947）.

Conclusion The SARS-CoV-2 strain is isolated from the fecal samples of COVID-19 cases and is confirmed by genomic sequencing and immunofluorescence test， which indicates the presence of live virus in feces of COVID-19 cases.