This document discusses virus taxonomy and classification. It provides: 1. An overview of virus classification systems, which are primarily based on phenotypic characteristics like morphology, nucleic acid type, host, and disease symptoms. 2. A history of virus naming conventions from early systems based on host names to current standardized systems like ICTV and Baltimore classifications. 3. Details on the International Committee on Taxonomy of Viruses (ICTV) which develops agreed-upon virus taxonomy, names, and classifications communicated internationally.

1. Nomenclature and
classification of viruses
N. H. SHANKAR REDDY
Ph.D., Plant Pathology
Annamalai University

2. • Virus taxonomy is for naming of viruses and placing them into a taxonomic system
• Virus mainly classified based on phenotypic characters (morphology, nucleic acid type,
host organism, mode of replication and type of disease they cause)
Purpose of taxonomy
• To make structural arrangements for easy understandings
• To able to communicate with each other
• Identifying the properties and nature of new viruses
• Study of evolutionally relationships

3. Johnson (1927)
• Adding the name virus and a number to the common name for the host
• Eg - Tobacco virus 1
K M Smith (1937)
• Named and grouped according to the generic name of the host
• Eg - Nicotiana virus 1
Holmes (1939)
• Latin binomial system of naming based on host reaction & method of
transmission
• Eg - Marmor tabaci, Holmes
1940 to 1966
• A generally accepted system of nomenclature & classification could be
• developed through international co-operation & agreement

4. What is the need for nomenclature and classification?
1. It gives a structural arrangement – understanding is easy
2. It helps in communication between virologists
3. It enables properties of new viruses to be predicted
4. It reveals the possible evolutionary relationships
Early naming is based on host and most important symptom
• Eg. Tobacco mosaic virus

5. At present they are two schemes for classification of
viruses
1. International committee on taxonomy of viruses (ICTV)
2. Baltimore classification
ICTV
International committee on nomenclature of viruses (ICNV, 1966) was
renamed as International committee on taxonomy of viruses (ICTV, 1973)
• By 2012, 7 orders, 96 families, 22 subfamilies, 420 genera, and 2618 species
has been identified by ICTV.

6. ICTV classification
Began to devise and implement rules for the naming and classification of viruses
early in the 1990s
order (-virales)
Family (-viridae)
Subfamily (-virinae)
Genus (-virus)
Phylum – mycota
Sub-phylum – mycotina
Class – mycetes
Order – ales
Family – aceae

7. ICTV ….1973
• To develop internationally agreed taxonomy of viruses
• To develop internationally agreed names for virus taxa
• To communicate the virus taxonomic decisions to the international community of
virologists
• To maintain an index of agreed names of virus taxa

8. Baltimore classification

10. The designation of abbreviations is based on
1. Abbreviation should be as simple as possible
2. It must not be duplicate
3. The word “virus” in a name is abbreviated as “V”
• The word “viroid” as “Vd”
4. Mosaic – M; Mottle – Mo
• Eg. Cowpea mosaic virus – CPMV; Cowpea mottle virus – CPMoV
5. Ringspot – “RS” in many cases, sometime “R”
6. Symptomless – “SL” in many cases, sometime “S”
7. The second / third lr in lower case represent host
• Eg - CdMV – Cardamom mosaic virus

11. 8. Sometime as two capital as exception
• Eg CPRMV – Cowpea rugose mosaic virus
9. Abbreviation for single word should not exceed 2 lrs
10. Secondary lr in abbreviation are omitted when their use would make the abbreviation
excessively long, generally more than 5 lrs CGMMV – CGMoMV - Cucumber
green mottle mosaic virus
11. Geographic region as TYLCV-Th
12. Associated virus – GLRaV-3
13. The names of virus orders, families, subfamilies, genera and species should be
written in italics with the first letter capitalized.
14. Other words are not capitalized unless they are proper nouns,
• e.g. Tobacco mosaic virus, Poliovirus, Murray River encephalitis virus.

12. Rules for naming viruses
Rules pertaining to genus
• A genus is a group of species sharing certain common characters.
• A genus name shall be a single word ending in "...virus”
• Approval of a new genus name must be linked to approval of a type species.
Rules pertaining to subfamily
• A subfamily is a group of genera sharing certain common characters.
• used when needed to solve a complex hierarchical problem
A subfamily name shall be a single word ending in "...virinae

13. Rules pertaining to family
• A family is a group of genera (whether or not these are organized into
• subfamilies) sharing certain common characters
• A family name shall be a single word ending in ..viridae”
• Approval of a new family name must be linked to approval of a type genus
Rules pertaining to order
• An order is a group of families sharing certain common characters
• An order name shall be a single word ending in "...virales”

14. Video available at you tube
Channel – Geeky Researcher