Abstract: A kit for visually detecting the presence of a virus in a direct clinical specimen is provided. The kit employs a rapid and direct assay for visually detecting a virus having a characteristic enzyme in a direct clinical sample without the need for any culturing step, This assay contains the following steps: (1) the clinical sample is contacted in solution with a substrate for the enzyme which includes a chromogen that is cleaved from the substrate by the enzyme and a precipitating agent which reacts with the liberated chromogen to form a precipitate, (2) the precipitate is concentrated, and (3) the concentrated precipitate is visually observed for the characteristic color of the chromogen. The observance of the characteristic color confirms the presence of the virus in the clinical specimen.

Abstract: Chromogenic derivatives of N-acetylneuraminic acid modified in the 4-position to contain a hydrogen atom, a fluorine atom, a methoxy group, or an ethoxy group are used as substrates in colorimetric assays for human influenza neuraminidase activity in clinical specimens for the purpose of selectively diagnosing influenza infection. The substrates may exhibit different reactivity with the different types of influenza neuraminidases, thus enabling one to discern the specific type of influenza infection and prescribe appropriate treatment and/or supportive therapy therefor.

Abstract: A rapid and direct assay for detecting of a virus having a characteristic enzyme in clinical samples in which (1) the clinical sample is contacted in solution with a substrate for the enzyme which includes a chromogen that is cleaved from the substrate by the enzyme and a precipitating agent that reacts with the liberated chromogen to form a precipitate (2) filtering the solution to concentrate the precipitate and (3) visually observing the concentrated precipitate for the characteristic color of the chromogen.