The CDC has admitted there are no covid19 virus isolates available as shown on Page 39 of this document. The Covid19 (PCR) tests are based stocks of invitro genetic sequences created in labs, not from an isolated virus.
https://www.fda.gov/media/134922/download
Peer reviewed paper: “Novel coronavirus (2019-nCoV) poses a challenge for public health laboratories as virus isolates are unavailable..” https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.3.2000045