Fig. 5

Cross-reactivity test results of the dual-mode SERS-LFA strip against SARS-CoV-2 and influenza A virus. Normalized intensity variations of SERS-LFA (Raman peak intensity at 1615 cm^− 1), ELISA (absorbance intensity), and colorimetric LFA (phase contrast intensity) for a SARS-CoV-2 (0–1000 PFU/mL) and b influenza A virus (0–8064 HAU/mL). c SERS intensity ratio variations of test lines 1 and 2 when the SARS-CoV-2 concentration was changed in the range of 50–1000 PFU/mL, but the concentration of influenza A virus was fixed at 8064 HAU/mL. d SERS intensity ratio variations of test lines 1 and 2 when the influenza A virus concentration was changed in the 168–8064 HAU/mL range, but the concentration of SARS-CoV-2 was fixed at 200 PFU/mL