**10. Taxonomy of viruses**

The definition of a virus 'species' is: "A virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche" [69]. A virus isolate can refer to any virus as long as the virus has existed for some time. Viruses are not considered to be either prokaryotes or eukaryotes but have implication from health point of view; hence characterization of viruses has increased considerably. Where earlier, only electron microsco‐ py was used, today sequencing of viral genomes constitutes advancements and the database is increasing. According to International Committee on Taxonomy of Viruses (ICTV), propos‐ als are afoot to accept online descriptions of viral taxa based on taxonomical details such as : dsDNA, ssDNA, rtDNA, rtRNA, dsRNA, ssNRNA, ssPRNA, SAT (Satellites), VIR (Viroids), UN (unassigned).
