Figure 4.

Relation of detection of replication-competent SARS-CoV-2 and estimated concentration of SARS-CoV-2 RNA to time from symptom onset. Among a total of 529 respiratory specimens, we evaluated 221 specimens that yielded positive RT-qPCR results and interpretable viral culture results (positive or negative) to assess the relation. Genomic RNA concentration was estimated using an internally validated calibration curve: Cn = −1.786 ln(viral load in log₁₀ RNA ge/mL) + 37.416. See Methods for details. Not shown is a specimen collected on day 133 after symptom onset with Cn value 31 and negative SARS-CoV-2 culture result. Abbreviations: Cn, cycle number; ge, genome equivalents; RT-qPCR, reverse transcription–quantitative polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.