We first evaluated the duration of QD-LFIAS detection. H5 and
H9 subtype viruses with concentrations of 16 HAU were added to
the sample pad, and the fluorescence of QDs was measured every
minute from 3 to 50 min. Fig. 3 shows that the fluorescence in-
tensity of QDs from both the H9 and H5 samples dramatically
increased from 3 min to 15 min, but this decrease was attenuated
as the detection time was extended further and the fluorescence
signal ultimately reached a plateau. Therefore, the optimum de-
tection time is 15 min after the addition of the sample. General
PCR-based influenza virus detection requires several hours to
complete the procedure, whereas the QD-LFIAS can be completed
in less than 20 min.