Fig. 1.

Quantitative RT-PCR assay for SARS-CoV: (A) Standard curve for quantitative analysis of ORF 1b of SARS-CoV. The threshold cycle (Ct) is the number of PCR cycles required for the fluorescent intensity of the reaction to reach a predefined threshold. The Ct is inversely proportional to the logarithm of the starting concentration of the input target. The correlation coefficient (R²) between these two parameters is shown. (B) An amplification plot of fluorescence intensity against the PCR cycle. The fluorescence signals for positive and negative samples are indicated. The X-axis denotes the cycle number of a quantitative PCR assay. The Y-axis denotes the fluorescence intensity.