This document classifies viruses into 7 groups based on their nucleic acid composition and transcription mechanism: 1. Group 1 contains dsDNA viruses like adenoviruses and herpes viruses. mRNA is synthesized using the dsDNA genome as a template. 2. Group 2 contains ssDNA viruses like parvoviruses. 3. Group 3 contains (+) sense ssRNA viruses which replicate in the cytoplasm, such as coronaviruses, picornaviruses, and togaviruses that cause diseases. 4. Group 4 contains (-) sense ssRNA viruses like rhabdoviruses and orthomyxoviruses. 5. Group 5 contains dsRNA

1. Dr. J. B. Kathiriya

12. THE BALTIMORE CLASSIFICATION OF VIRUSES
Animal viruses are classified in the following 7 groups
according to relationship between virion, nucleic acid
& mRNA transcription :
Group1. ds DNA viruses
Group2. ss DNA viruses
Group3. ds RNAviruses
Group4. (+) sense ss RNAviruses
Group5. (-) sense ss RNAviruses
Group6. ss RNA reverse transcribing viruses
Group7. ds DNA reverse transcribingviruses

15. Group1. ds DNA viruses:the mRNA
is synthesized on a ds DNA genome
template.following are eg. Of some
viruses 1. adenoviruses
2.herpes virus
3. papovavirus
4. poxvirus

16. 1. Adenoviruses
•virions are naked ,
non enveloped. 90-100
nm diameter & have
icosahedral symmetry.
•The penton fiberswith
a globular head are
involved in the process
of attachment of the
virus to the hostcell.
•Hexons consists of
protein II with a central
core, invoved in the
stabilization & assembly
of particles.

17. Diseases caused by adenoviruses are :
1. respiratory disease
2.conjunctival pneumonia
3.acute hemorrhagic cyctitis
4.acute gastroenteritis

18. 2.Herpes virus
•The nucleocapsid is spherical
icosahedral &100 nm in
diameter , enclosed in
glycoprotein lipid envelop.
•Glycoprotein are visible as
“spikes” that are projected from
thesurface.
•The nucleic acid is linear ds
DNA which is converted intoa
circular DNA molecule upon
slight digestion.
•Disease caused by herpesvirus
: herpes simplex I ( cold sores),
herpes simplex II (genitalsores)
& varicellovirus (chickenpox.
Shingles) .

19. 3. Papovavirus
•Capsid is of 45-55 nm
diameter, naked ,
icosahedral, virion
consists of DNA &
protein. capsid is made
up of 72 capsomers.
•Virus enter the cell &
migrates to thenucleus
forreplication.
•Disease:
•Papilomavirus (cervical
cancer,human warts)
•Polyomavirus (cause
tumor in mice)

20. 4. poxvirus
•Poxvirus are brick
shaped (240-
300nm),dsDNAgenome
(130-260kb) & naturally
associated withenzyme
•Virions are enveloped .
Viral multiplication is
started by viral
transcriptase, the viral
components are
synthesized & assemble
in the cytoplasm of the
hostcell.
•Pathogenesis:
•Human monkey pox
•Smallpox (variolavirus)

21. Grpoup 2. ssDNA
virus: parvovirus
•Parvovirus are linear,
average genome sizeof
5000 nucleotide,
smallest virus with 18-
28 nm diameter.
•Viral capsid s madeup
of 2-4 protein form
naked icosahedral
structure.
•Diseases:
•Human parvovirusB19
•Erythema infectiosum
•Joint diseasesyndrome

22. Group3. (+) ss RNA
virus:1. corona virus
•Corona virus are
enveloped, helical & 60-
200 nm
diameter.genomes size
are 16-21kb.
•it replicates inthe
cytoplasm.
•Diseases :
•Respiratorysyndrome
•Severe acute
respiratory syndrome

23. 2.Picorna virus
Virions naked
,icosahedral. Capsid is
composed of 60 copies of 4
structiural protein .
Viral genome are linear
7.1-8.9 kb size
Diseases: poliovirus
(polio)
Rihinovirus( common
cold)
Hepatitis Avirus
(hepatitis A)

24. 3.Togavirus
•Envelop consists of 80
trimer spikes . The spikes
consists of glycoprotein
that help in attachment
protein to receptor of
host cell membrane.
•Eg. Alphavirus
•Eastern equine
encephalitisvirus
•Yellow fevervirus
•Rubellavirus

25. Group 4. (-) ssRNA
viruses
1.Rhabdovirus
Envelop with spikes
made upof gly coprotein
linked matrix protein
contain nucleocapsid
Eg. Mumps virus ,
Rabies virus

26. 2. Orthomyxo virus

27. Group 5. ds RNA virus :eg. reovirus
Group6. ss RNA RT virus :eg.reterovirus
Group 7. ds DNA RT virus: eg Hepadna
virus.