Enzymatic diagnostic test for SARS and other viral diseases

A method for determining the presence of a Nidovirus or Picornavirus virus in a sample suspected of containing said virus, the method comprising:

• Contacting a sample with a substrate peptide comprising at least four amino acid residues and capable of being cleaved at a cleavage point by an enzyme to form a cleaved first peptide fragment and a second peptide fragment;
• and
• detecting the virus by observing the signal from a signaling moiety linked to the substrate peptide;
• wherein the enzyme is encoded by nucleic acid of the virus and is present in the sample;
• wherein said substrate peptide comprises an amino acid sequence identical to a sequence of a polyprotein cleavage region of said enzyme and including said cleavage point;
• wherein said peptide cleavage fragments are peptide fragments of the substrate peptide;
• wherein a signaling moiety is linked to a portion of the peptide present in the first peptide fragment;
• and
• wherein said method is a heterogeneous assay method.