The practical need to partition the world of the viruses into distinguishable, universally agreed upon entities is the ultimate justification for developing a virus classification system. The first internationally organized attempts to introduce some order in the bewildering variety of viruses took place at the International Congress of Microbiology held in Moscow in 1966. A committee, later called The International Committee on Taxonomy of Viruses (ICTV) was created which was given the task of developing a single, universal taxonomic scheme for all the viruses infecting animals (vertebrates, invertebrates and protozoa), plants (higher plants and algae), fungi, bacteria and archaea. Since 1971 the ICTV, operating on behalf of the world community of virologists, has produced the following six reports describing the current state of virus taxonomy:


ICTV Report	Editors	Reporting ICTV Proceedings at the International Congresses of Virology held in:

The First Report, 1971	P. Wildy	Helsinki, 1968
The Second Report, 1976	F. Fenner	Budapest, 1971 and Madrid, 1975
The Third Report, 1979	R.E.F. Mathews	The Hague, 1978
The Fourth Report, 1982	R.E.F. Mathews	Strasbourg, 1981
The Fifth Report, 1991	R.I.B. Francki, C.M. Fauquet, D.L. Knudson, F. Brown	Sendai, 1984; Edmonton, 1987 and Berlin, 1990
The Sixth Report, 1995	F.A. Murphy, C.M. Fauquet, D.H.L. Bishop, S.A. Ghabrial, A.W. Jarvis, G.P. Martelli, M.A. Mayo, M.D. Summers	Glasgow, 1993

The present Seventh Report of the ICTV builds on the accumulated taxonomic construction of its predecessors and records the proceedings of the Committee since 1995, including decisions reached at the Tenth International Congress of Virology held in Jerusalem in 1996 and at midterm meetings in 1997 and 1998.

In 1991, the ICTV agreed that the hierarchical level of species would be defined and added to the categories of genus, subfamily, family and order which were already in use in the universal virus classification system. In this Seventh Report, the list of recognized virus species has been further extended and the demarcation criteria used to discriminate between individual virus species in different genera have been spelled out as far as possible. This work is still incomplete and will continue to require the input of the more than 50 Study Groups that provide the information codified in ICTV Reports. The present Report represents the work of more than 500 virologists world-wide, i.e., the members of the study groups, subcommittees and the Executive Committee of the ICTV. The compilers of the Report wish to express their gratitude to all these virologists.

We are especially grateful to Dr. Claude M. Fauquet, his secretary Ms. Ella Blanc, and his staff (Camillo Orozco, Adrien Fauquet and Emilie Fauquet) for taking responsibility for the typing, formatting, and layout of the Seventh ICTV Report and for the drawing and scanning of all the diagrams and pictures.

For the Committee,

Marc H. V. Van Regenmortel

President of the International Committee on Taxonomy of Viruses