question: What do we know about detection of SARS-CoV-2 RNA after clinical recovery from COVID-19?
answer: Many recovered persons do not have detectable SARS-CoV-2 RNA in upper respiratory tract specimens. However, viral RNA can be persistently detected by reverse transcription polymerase chain reaction (RT-PCR) in respiratory tract samples in some persons after apparent clinical recovery.  In some persons, after testing negative by RT-PCR in two consecutive samples, later samples can test positive again. These persistent detections of viral RNA usually are associated with higher cycle threshold (Ct) values (i.e., fewer RNA copies) than Ct values found in RT-PCR results from samples collected shortly before or during clinical illness. Studies that have examined how long SARS-CoV-2 RNA can be detected in adults have demonstrated that, in some persons, it can be detected for weeks.