Complexities of Viral Nomenclature

No consistent system for naming viruses – some are named for the:• associated diseases (e.g. poliovirus, rabies virus)• specific type of disease they cause (e.g. hepatitis A,B,C, D, E)• sites in the body that are affected or from which they were first

isolated (e. g. rhinovirus and adenovirus) • geographic locations in which they were first isolated (e.g. Sendai

virus [Sendai, Japan] and Coxsackievirus [Coxsackie, New york]) • sicentists who first discovered them (e.g. Epstein-Barr virus)• way in which people imagined they were contracted (e.g. dengue,

for “evil spirit” and influenza, for the “influence of bad air)• combinations (e.g. Rous sarcoma virus)

International Committee on Taxonomy of Viruses (ICTV)

• member group of the International Union of Microbiological Societies

• oversees the ongoing process of devising and maintaining a universal classification scheme for viruses

• Assigns viruses to orders, families, subfamilies, genera, and species based on information provided by study groups composed of experts on specific types of viruses.

David Baltimore developed a system to classify viruses based on their

genomes…The Baltimore System…

VII

I. dsDNA

II. ssDNA

III. dsRNA

IV. ss (+) RNA

V. ss (-) RNA

VI. ss (+) RNA with DNA intermediate

VII. gapped dsDNA

Virus Classification

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Classical hierarchical system:

Kingdom

Phylum

Class

Order - virales

Family (-viridae)

Genus (-virus)

Species

Virus ClassificationOrder: viralesFamily: Filoviridae

Enveloped virions, variably elongated filaments 650–1,400 nm in length and pleomorphic in shape, containing a helical nucleocapsid with single-stranded negative-sense RNA (about 19 kilobases in length) and an endogenous RNA polymerase.

Genera:• Filovirus : contains the Marburg viruses• Ebolavirus: contains the Ebola viruses.

Species (Strain):Ebolavirus: Ebola-Zaire, Ebola-Sudan, Ebola-Cote d’Ivoire, Ebola-Reston, Ebola-Bundibugyo

Extremely stable, resistant to heat, detergents and chlorination

All DNA viruses except the Parvoviridae are dsDNA

DNA Virus Mnemonic "HHAPPPPy", -Hepadna -Herpes -Adeno -Pox -Parvo -Papilloma -Polyoma

All RNA viruses except Reoviridae are ssRNA

A 27 y/o worker at a day care center has recently been feeling tired, has a slight fever, and has felt nauseated and vomited several times. Yesterday, she had abdominal pain and chills, and today she voided dark urine. Lab tests for serum enzymes indicated elevated AST and ALT. No infectious agent could be grown in culture, but PCR testing determined that the causative agent contains a positive sense, Single Stranded RNA genome. Electron microscopy revealed a naked icosahedral capsid approximately 28 nm in diameter. The virus responsible for the infection belongs to the family: 1. Hepadnaviridae

2. Flaviviridae

3. Picornaviridae

4. Polyomaviridae

A 27 y/o worker at a day care center has recently been feeling tired, has a slight fever, and has felt nauseated and vomited several times. Yesterday, she had abdominal pain and chills, and today she voided dark urine. Lab tests for serum enzymes indicated elevated AST and ALT. No infectious agent could be grown in culture, but PCR testing determined that the causative agent contains a positive sense, Single Stranded RNA genome. Electron microscopy revealed a naked icosahedral capsid approximately 28 nm in diameter. The virus responsible for the infection belongs to the family: 1. Hepadnaviridae

2. Flaviviridae

3. Picornaviridae

4. Polyomaviridae

Which of the following statements is correct?

1. Viruses can have an icosahedral capsid or an envelope, but not both.

2. Helical capsids are always surrounded by an envelope.

3. Icosahedral capsids are only found among DNA viruses.

4. Icosahedral capsids are very large.

Which of the following statements about human viruses is correct?

1. Viruses can have an icosahedral capsid or an envelope, but not both.

2. Helical capsids are always surrounded by an envelope.

3. Icosahedral capsids are only found among DNA viruses.

4. Icosahedral capsids are very large.