Primer screening and RF-RT-RAA assay establishment. (A) Agarose gel electrophoresis results of RT-RAA products using different primer pairs. M: DL2000 DNA marker; 1, 3, 5: Positive reactions using primer pairs of ORF6 F1/ORF6 R1, ORF6 F2/ORF6 R2, ORF6 F3/ORF6 R3, respectively; 2, 4, 6: Negative controls for primer pairs of ORF6 F1/ORF6 R1, ORF6 F2/ORF6 R2, ORF6 F3/ORF6 R3, respectively. (B) Amplification results of RF-RT-RAA through real-time fluorescence read-out. (C) Amplicons of RF-RT-RAA observed with the naked eye under blue light. The image was captured by a mobile phone camera. Curve or tube 1: Positive reaction using the primer pair ORF6 F1/ORF6 R1 and a probe; curve or tube 2: Negative control.