Abstract: Chromogenic and fluorogenic 4,7-dialkoxy-N-acetylneuraminic acid substrates of the general formula ##STR1## are provided wherein R.sub.1 and R.sub.2 are alkyl groups containing 1 to 4 carbon atoms and R.sub.3 is a chromogenic or fluorogenic group. These substrates can be used to detect influenza types A and B in clinical samples or specimens. More particularly, these 4,7-dialkoxy-N-acetylneuraminic acid substrates can be used to distinguish between various viruses having neuraminidase reactivity. Thus, influenza type A and B viruses can be distinguished from parainfluenza type 1, 2, 3, and 4, and mumps using the 4,7-dialkoxy-N-acetylneuraminic acid derivatives of this invention. Diagnostic methods employing these substrates are provided to identify influenza type A and B viruses in clinical specimens and to distinguish from other viruses having neuraminidase reactivity.