virus taxonomy and classification

1. VIRUS TAXONOMY AND
CLASSIFICATION
BY
DR JAWAD NAZIR
ASSISTANT PROFESSOR
DEPARTMENT OF MICROBIOLOGY
UNIVERSITY OF VETERINARY AND ANIMAL SCIENCES, LAHORE

2. Virus Taxonomy
Taxonomy and classification
 Science of grouping and naming of living organisms
 Universally accepted identical system
 Shows relationships among organisms
 Is a way to provide identification of an organism
 Phylogeny: The study of the evolutionary history of
organisms.

3. Virus Taxonomy
Linnean Taxonomy
 Carl linnaeus (1707-1778)
 Systema Naturae
 Father of modern taxonomy
 Grouping of all of the organisms
on the earth
 Binomial nomenclature
Genus-specie

4. Virus Taxonomy
Virus taxonomy
 Early virus classification was based upon the
pathogenic effects and transmission patterns
 Hepatitis viruses
 Hepatitis A: Picornavirus
 Hepatitis B: Hepadnavirus
 Hepatitis C: Flavivirus
 In 1930 , virus structure and composition details
start to emerge that made possible to group viruses
on the basis of shared features of viruses

5. Virus Taxonomy
Virus taxonomy
 In 1966, International committee for nomenclature of viruses (ICNV) was
developed
 In 1973, International committee for taxonomy of viruses (ICTV) was
established
 ICTV governed by the virology division of the International union of
Microbiological societies
 Experts meet time to time to reconsider and revise the virus taxonomy
and nomenclature
 Most recent report was published in 2011 “9th report”
 Available online http://www.ictvonline.org/

6. Virus Taxonomy
Recent criteria for classification
 Type and character of viral genome
 Strategy of viral replication
 Structure of virus
Additional information by sequencing or partial
sequencing of viral genome

7. Virus Taxonomy
Virus taxonomy
 Five main hierarchical levels
 Order
 Family
 Subfamily
 Genus
 Specie

8. Virus Taxonomy
Virus taxonomy
 Two orders
 Mononegavirales
 Nidovirales
Paramyxoviridae
Rhabdoviridae
Bornaviridae
Filoviridae
Coronaviridae
Arteriviridae

9. Virus Taxonomy
Most recent classification (last updated in 2014)
Seven orders and an unassigned group
 Caudovirales (3 families)
 Herpesvirales (3 families)
 Ligamenvirales (2 families)
 Mononegavirales (5 families)
 Nidovirales (4 families)
 Picornavirales (5 families)
 Tymovirales (4 families)
 Unassigned group (78 families)
Virus taxonomy

10. Virus Taxonomy
 More than 50 families and 22 are of veterinary
importance
 230 genera
 More than 1500 species
 More than 30,000 different strains
Virus taxonomy

11. Virus Taxonomy
Most recent classification (last updated in 2014)
 07 orders
 104 Families
 23 Subfamilies
 505 Genera
 3186 Species
Virus taxonomy

12. Virus Taxonomy
Virus Specie?
In 1991, ICTV accepted the definition by van
Regenmortel which states that
“A virus species is defined as a polythetic class of viruses that
constitutes a replicating lineage and occupies a particular
ecological niche”

13. Virus Taxonomy
Nomenclature
Naming viruses
First name of virus order, family, subfamily, and genus is
capitalized while the complete name is italicized
Specie name:
 In context to taxonomy: Canine distemper virus
 In context to tangible properties: not capitalized (un-
till started from a city or name or place) nor italicized
canine distemper virus

14. Virus Taxonomy
Nomenclature
Designation Suffix
Order (-virales)
Family (-viridae)
Subfamily (-virinae)
Genus (-virus)

15. Virus Taxonomy
Nomenclature

16. Virus Taxonomy
Further lower taxonomy
 Strain
 Subtype
 Variant
 Serotype
 Pathotype
 Genotype
 Clade
No universal definition or formal nomenclature are
recognized for strains and subtypes

17. Virus Taxonomy
Further lower taxonomy
 Lentogenic: Non pathogenic
 Mesogenic: Mild
 Velogenic: High
 LPAI: Low pathogenicity avian influenza
 HPAI: High pathogenicity

18. Virus Taxonomy
Baltimore classification

19. Virus Taxonomy
Virus Quasispecies
Each virus exist as a genetically diverse, rapidly
evolving population of virions with non-identical
but closely related mutant and recombinant viral
genomes based on a consensus sequence.

20. Virus Taxonomy
Quasispecies distribution of HBV and HCV

21. Virus Taxonomy
How viruses are named
Based on:
- the disease they cause
poliovirus, rabies virus
- the type of disease
Hydropericardium syndrome
- geographic locations
Newcastle disease virus
- their discovers
Epstein-Barr virus
- how they were originally thought to be contracted
influenza virus (the “influence” of bad air)

22. Virus Taxonomy
Grouping of viruses on the basis of
epidemiological criteria
 Enteric viruses
 Respiratory viruses
 Arboviruses (arthropod borne viruses)
 Oncogenic viruses

23. THANK YOU