This document discusses the classification of viruses based on 8 criteria: nucleic acid type, structure, site of replication, host range, transmission method, presence or absence of an envelope, capsid structure, and the Baltimore classification system. Viruses can be classified as DNA viruses, RNA viruses, or DNA-RNA viruses depending on whether their genetic material is DNA, RNA, or both. They can also be classified based on their structure (such as helical or icosahedral), where in the host cell they replicate, which organisms they infect as hosts, how they are transmitted, whether they have an envelope, and capsid structure.

1. P.AARTHY
III B.SC MICROBIOLOGY

2.  Infectious microbe
 Acellular organism
 Microscopic (smaller than
bacteria)
 Obligate Parasite
 Replicate inside host
 Covered by Capsid(Protein coat)

3. 1. Based on Nucleic acid
2. Based on Structure
3. Based on replication properties & site of replication
4. Based on Host range
5. Based on mode of Transmission
6. Based on Envelope
7. Based on Capsid structure
8. Baltimore classification

4. 1. BASED ON NUCLEIC ACID:
DNA virus
• Genetic material- DNA
• Double stranded DNA- Adeno virus, Herpes virus
• Single stranded DNA- Parvo virus
RNA virus
• Genetic material- RNA
• Double stranded RNA- Reovirus
• Single stranded RNA-
• +RNA - Polio virus, Hepatitis A -RNA - Rabies virus, Influenza
virus
DNA-RNA
virus
• Genetic material- DNA & RNA
• Leukoviruses & Rous’s viruses (RNA tumor viruses)

5. 2. BASED ON STRUCTURE:
Cubical:
Reovirus
Spiral:
Orthomyxovirus
Radial
symmetry:
Bacteriophage
Complex:
Pox virus

6. 3. BASED ON REPLICATION PROPERTY AND SIZE OF REPLICATION:
• Poliovirus, Rhinovirus
Replication & assembly in
cytoplasm of host
• Poxvirus, Influenza virus
Replication in nucleus &
assembly in cytoplasm of host
• Parvo virus, Adeno virus
Replication & assembly in
nucleus of host
• Hepatitis B virus, Herpes virus
Virus replication through ds
DNA intermediate
• Polio virus, HIV
Virus replication through ss
RNA intermediate

7. 4. BASED ON HOST RANGE:
Bacteriophage - virus
infecting bacteria. Lambda
phage, T4 bacteriophage
Plant virus - Virus
infecting plants. TMV
Animal virus - Virus
infecting animal. Polio
virus, Adeno virus
Insect virus – virus
infecting insects.
Baculovirus, Granulosis
Fungal virus – virus
infecting fungi. Aspergillus
fumigatus

8. 5. BASED ON MODE OF TRANSMISSION:
Virus transmitted through respiratory route
• Swine flu , Rhinovirus
Virus transmitted through foeco - oral route
• Hepatitis A virus , Polio virus
Virus transmitted through sexual contact
• Retro virus
Virus transmitted through blood transfusion
• HIV
Zoonotic virus (through biting of infected animal)
• Rabies virus, Alpha virus

9. 6. BASED ON PRESENCE OR ABSENCE OF ENVELOPE:
Non-enveloped virus: (only
protein capsid) Adeno virus ,
Polio virus
Enveloped virus: (lipid bilayer)
Pox virus, HIV
Envelope- lipid containing membrane
surround some virus particle.

10. 7. BASED ON CAPSID STRUCTURE:
• Hepatitis A , polio virus
Naked
Icosahedral
• HIV-1, Rubella virus
Enveloped
Icosahedral
• Influenza virus, Mumps virus
Enveloped helical
• TMV, Filo virus
Naked helical
• Small pox virus, T4
bacteriophage
complex
Capsid- protein shell encloses their
genetic material

11. 8. BALTIMORE CLASSIFICATION:

12. REFERENCE:
1. https://www.bionity.com/en/encyclopedia/Virus_classification.html#Not
es
2. https://microbiologynotes.org/virus-introduction-properties-and-
classifications/
3. https://www.onlinebiologynotes.com/classification-of-virus/
4. https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kais
er)/Unit_4%3A_Eukaryotic_Microorganisms_and_Viruses/10%3A_Viruses
/10.04%3A_Classification_of_Viruses
5. https://microbenotes.com/classification-of-virus/