Arch Virol 146/1 (2001)
C. M. Fauquet
and M. A. Mayo
ILTAB/Danforth Plant Science Center, University of Missouri St. Louis, St. Louis, Missouri, U.S.A.
Scottish Crop Research Institute, Dundee, U.K.
After an unexpected and much regretted delay, the seventh Report of the International
Committee on Taxonomy of Viruses (ICTV)  has been published. The Report is the
culmination of the efforts of the many virologists who have contributed to the diverse
committees and Study Groups that constitute the ICTV. Some 476 virologists from many
countries have been involved in various capacities during the interval following the
publication of the previous Report . The size, scope and content of the 7
reflections of the enormous increase in virological knowledge during the last 5 years; the
Report runs to 1162 pages that describe 3 Orders, 63 Families, 240 Genera. These compare
with the taxonomy described in the previous Report that comprised 1 Order, 50 Families
and 164 Genera. An important development since the 6
Report was published, has been a
focus on the demarcation of species within the genera . Previously, many viruses were
listed but it was not clear which belonged to distinct species and which were strains or other
sub-specific entities within a particular species. The current taxonomy  lists more than
3600 viruses among 1550 species.
New features in the 7
New families and genera
Fourteen new families are described in the 7
Report (Table 1). Some (e.g. Ascoviridae)
contain new genera and others contain genera that were previously listed as “unassigned” or
“floating” . One family (Papovaviridae) described in the 6
Report has been divided into
the new families Polyomaviridae and Papillomaviridae because of the profound differences
between viruses in what were two genera in a single family.
The new families contain genera of viruses that have genomes of 4 of the 6 major types.
Also, the classification has been extended to include viroids. These have been classified into
7 genera that are distributed among 2 families.
Other new genera have been classified into families that were already described in the
Report (Table 2). Some of these genera were formed by taking species out of their
previous genus in recognition of its having become too diverse to be classified as one genus,
some new genera were needed to classify novel virus species. Some of the genera listed in
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