(A_B) Vero E6-TMPRSS2 (A) or Vero E6 (B) cells were inoculated with a total of 126 clinical NP swab samples representing a range of viral RNA levels, both total E RNA (Clinical Sample E CT detected by WHO-E primer/probe set) and subgenomic E RNA (CT detected by the Mills-SgE primer set developed in this study). Culture supernatants were harvested when cells displayed CPE or at day 7 if no CPE was observed earlier, clarified, and presence (blue square) or absence (yellow circle) of SARS-CoV-2 determined by immuno-focus assay. 