Possible length of infectivity > 25 days after negative test.

Our data suggest the possibility of extended duration of viral shedding in faeces, for nearly 5 weeks after the patients' respiratory samples tested negative for SARS-CoV-2 RNA. Although knowledge about the viability of SARS-CoV-2 is limited,the virus could remain viable in the environment for days, which could lead to faecal–oral transmission, as seen with severe acute respiratory virus CoV and Middle East respiratory syndrome CoV

Prolonged presence of SARS-CoV-2 viral RNA in faecal samples Wu et al, The Lancet, March 2020