Taxonomy and Classification of Viruses

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This chapter discusses about taxonomy and classification of viruses. For viruses, the process of comparative analysis plays a critical role in increasing our overall knowledge of the molecular biology, pathogenesis, epidemiology, and evolution of poorly understood or newly isolated viruses. This knowledge enhances our ability to respond to new threats by supporting the development of diagnostics, vaccines, and other antiviral therapies. In fact, it is likely that viruses have multiple independent evolutionary origins that cannot be easily or completely separated from the evolution of their hosts, as they cannot reproduce or evolve separately from their hosts. Therefore, viruses might be better represented as individual twigs arising from branches spread throughout the rest of the tree. In addition to distinct evolutionary histories, viruses differ from other domains of life in the variety of possible coding molecules they utilize to store their genetic programs. For viruses, the Virology Division of the International Union of Microbiological Societies has charged the International Committee on Taxonomy of Viruses (ICTV) with the task of developing, refining, and maintaining a universal viral taxonomy. As categorized according to the 2009 ICTV taxonomy, viruses that infect humans fall into 4 orders: the Herpesvirales, Mononegavirales, Nidovirales, and Picornavirales. The ICTV produces an extensive amount of information during the process of classifying and naming viruses that is published regularly in the ICTV reports.