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Virus isolation in cell cultures, immunofluorescence-based ASSAY and molecular techniques to determine nucleic acid, have all been used successfully to detect and identify the viruses. On the other hand, the most commonly used methods to quantify viruses can be subdivided into three broader categories – techniques measuring viral infectivity (viral plaque assay, TCID50 and immunofluorescence FOCI assay), those that examine viral nucleic acid and protein (qPCR, immunoblotting, immunoprecipitation, ELISA and hemagglutination assay) and those that rely on direct counting of physical viral PARTICLES (viral flow cytometry and transmission electron microscopy). Since each of these established methods has several limitations (Table 1), improved techniques of virus identification and quantification, such as mass spectrometry [5] and next-generation sequencing/metagenomics [6, 7], are explored to OVERCOME their limitations. Here we discuss some of the most common virus identification and quantification protocols, currently being used both in experimental and diagnostic virology.

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