viruses are classified for ease of research and study over them.

1. Viral
Taxonomy
MICROBIOLOGY

2. INTRODUCTION
 Virus classification is the process of naming viruses and
placing them into a taxonomic system.
 Viruses are mainly classified by phenotypic
characteristics, such as morphology, nucleic acid type,
mode of replication, host organisms and the type of
diseases they cause.
 Currently there are two main scheme used for the
classification of viruses:
1. The international committee on taxonomy of viruses
(ICTV)
2. Baltimore classification.

3. INTERNATIONAL
COMMITTEE ON TAXONOMY
OF VIRUSES(ICTV)
 ICTV was established in 1966.
 The only body charged by the International Union of
Microbiological Societies with the task of developing,
refining, and maintaining a universal virus taxonomy.
 This system of nomenclature differs from other
taxonomic codes on several points.
 A minor point is that names of orders and families are
italicized, unlike in the International Code of
Nomenclature for algae, fungi, and plants and
International Code of Zoological Nomenclature.

4. ICTV (Contd.)
 In the most recent report of the ICTV, study
group members have listed the criteria that
identify each species, then listed species
according to the criteria.
 In addition, some viruses are listed as tentative
species because their taxonomic status cannot
currently be unambiguously determined.
 Last, a type species, the species used to define the
taxon, has been identified for each genus.

5. Objectives of ICTV
 To develop an internationally agreed taxonomy for
viruses.
 To develop internationally agreed names for virus
taxa, including species and sub-viral agents.
 To communicate taxonomic decisions to all users of
virus names, in particular the international
community of virologists.
 To maintain an index of virus names.
 To maintain ICTV database on internet, that records
the data that characterize each named viral taxon,
together will be the common names of each taxon in
all major languages.

6. ICTV’S ESSENTIAL
PRINCIPLES OF VIRUS
NOMENCLATURE
 Stability
 To avoid or reject the use of names which
might cause error or confusion.
 To avoid the unnecessary creation of
names.

7.  In July 2013, the ICTV definition of species changed
to state: “A species is a monophyletic group of
viruses whose properties can be distinguished from
those of other species by multiple criteria.”
 Viral classification starts at the level of order and
continues as follows, with the taxon suffixes given in
italics:
 Order (-virales)
 Family (-viridae)
 Subfamily (-virinae)
 Genus (-virus)
 Species
Species names generally take the form of [Disease]
virus.

8.  As an example, the full formal written
description of human respiratory syncytial
virus is
 Order: Mononegavirales
 Family: Paramyxoviridae
 Subfamily: Pneumovirinae
 Genus: Pneumovirus
 Species: Human respiratory syncytial virus

9. BALTIMORE CLASSIFICATION
 Named after DAVID BALTIMORE, a nobel prize
winning biologist.
 Baltimore classification (first defined in 1971) is a
classification system that places viruses into one of
seven groups depending on:
1. a combination of their nucleic acid (DNA or RNA)
2. strandedness (single-stranded or double-stranded),
3. Sense (+ or -)
4. method of replication.

10. BALTIMORE
CLASSIFICATION (Contd.)
 I: dsDNA viruses (eg. Adenoviruses, Poxviruses)
 II: ssDNA viruses (eg. Parvoviruses)
 III: dsRNA viruses(eg. Reoviruses)
 IV: (+)ssRNA (eg. Togaviruses)
 V: (-) ssRNA (eg. Rhabdoviruses)
 VI: ssRNA-RT viruses RNA with DNA
intermediate in life cycle.
 VII: dsRNA-RT viruses (eg. Hepadnaviruses)

11. BALTIMORE CLASSIFICATION

12. THANK YOU