Review on Classification and Nomenclature of Viruses

Abstract

Viruses are subcellular, infectious, non-living creatures that can only replicate and metabolize inside the cells of living hosts. Virus taxonomy is the classification of viruses into categories called taxa. The classification and nomenclature recently gained importance due to the exponentially increasing number of new viruses discovered. Hence the current review on classification and nomenclature of virus aimed to provide sufficient and updated information to readers. Current virus classification is increasingly performed using more complex phylogenetic approaches that move researchers closer to a rudimentary understanding of the origin, evolution, relatedness, and diversification of viruses. In the taxonomic hierarchy of virus, the highest taxa are real and the lowest rank is species. To categorize viruses, phenotypic traits like morphology, nucleic acid type, and mechanism of replication, host organisms, and the sort of disease they cause are taken into consideration. Mostly based on 1. Classical- e.g. Animal, plant, or bacterial virus system- e.g. Naked or enveloped virus. 2. Genomic-Baltimore classification by seven categories: I: dsDNA viruses (e.g. Adeno viruses, Herpes viruses, Pox viruses) II: ssDNA viruses (+ strand or "sense") DNA (e.g. Parvo viruses) III: dsRNA viruses (e.g. Reo viruses) IV: (+) ssRNA viruses (+ strand or sense) RNA (e.g. Corona viruses, Picorna viruses, Toga viruses) V: (−) ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxo viruses, Rhabdo viruses). VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retro viruses). VII: dsDNA-RT viruses DNA with RNA intermediate in life-cycle (e.g. Hepadna viruses). 3. Serology (a corona virus). There isn't a standardized format for virus species names yet, in contrast to the binomial nomenclature used for cellular species. The ICTV now requires that a species name comprise as few words as possible while still being distinct, and must not merely contain the term virus and the host. By responding to a series of questions based on contrasting traits, a species can be identified using the dichotomous key method.