Virology Division News
Virology Division News
Arch Virol 144/2 (1999)
Virus Taxonomy – 1999
The Universal System of Virus Taxonomy, updated to include the new proposals
ratified by the International Committee on Taxonomy of Viruses during 1998
C. R. Pringle
Department of Biological Sciences, University of Warwick, Coventry, U.K.
A condensed version of the Universal System of Virus Taxonomy was published in
Virology Division News at the beginning of 1998 . Since then, several new taxonomic
proposals from Study Groups have been considered by the Executive Committee of the
International Committee on Virus Taxonomy (ICTV) . These proposals have now been
ratified by postal ballot of the full membership of the ICTV, as required by the Statutes of
the ICTV. The Table below presents the current revision of the Universal System of Virus
Taxonomy, including all the new taxonomic proposals ratified by the ICTV since publica-
tion of the Sixth Report in 1995 . This condensed version of the Universal Taxonomy
lists Orders, Families, Genera and Type species, but does not extend to the listing of
approved virus species. The complete taxonomy will be published as the Seventh Report of
the ICTV prior to the Eleventh International Congress of Virology in Sydney in 1999.
The order of presentation of virus taxa follows the convention adopted in the Sixth
Report [4, 5]. It is based on four criteria: (1) the nature of the viral genome, (2) the
strandedness of the viral genome, (3) the facility for reverse transcription, and (4) the
polarity of the virus genome. The order of presentation does not imply any hierarchical or
phylogenetic relationship. At present viruses are classified into 233 genera. Of these, 204
are classified into 64 families. The remaining 29 are unassigned (previously designated
“floating”) genera which have yet to be assigned to a higher taxon. Three Orders are
recognised now: the order Caudovirales , which includes the families Myoviridae,
Siphoviridae and Podoviridae; the order Mononegavirales , which includes the four
families Bornaviridae, Filoviridae, Paramyxoviridae and Rhabdoviridae; and the order
Nidovirales , which includes the two families Coronaviridae and Arteriviridae.
The ICTV aims to eliminate all remaining vernacular names from the Universal
Taxonomy and replace them by international names. However, a few taxa retain the
designation “… -like viruses”. This may represent a situation where the name favoured
by a Study Group has been rejected because it does not conform to the current Rules of
Nomenclature of the ICTV . Or more usually it is a consequence of unresolved indeci-
sion concerning the definitive criteria for designation of a species.
A major change in orthography was ratified by the ICTV in 1998 to bring virus taxonomy
into line with other taxonomic systems [3, 4]. In future the names of all virus species will be
given in italics with the initial letter capitalised. The names of viruses having the status of
tentative species will not be given in italics, but will have the initial letter capitalised.