THz optical properties for various types of virus samples. (a) Normalized THz transmission spectra measured using the single-resonance nano-antenna without virus sample (black), and with selected three viruses, H1N1 (blue), H5N2 (cyan), and H9N2 (magenta). (b) FDTD simulation results of transmittances for the single-resonance nano-antenna and the three different model samples with various composition of dielectric constants (n and κ) are shown. Inset indicates a used geometry for simulation.