University of Michigan - Ann Arbor

University of California, Davis

The study of viruses and virus like agents. It deals heavily in their structure, classification, evolution, method of infection, effects of infection and how to cure or treat the infections.

Virology

The virology of COVID-19: How viruses infect host cells in the body

Virology of COVID-19

Focuses of Virology

The International Committee on Taxonomy of Viruses (ICTV) developed a universal nomenclature system that categorizes viruses into families and genera. This taxonomy groups viruses based on their genetics, chemistry, morphology, and mechanism of multiplication, rather than using the standard binomial nomenclature system. Under this system, viral family names end with the suffix *-viridae* (e.g., *Parvoviridae*) and genus names end with *-virus* (e.g., *Parvovirus*), with orders, families, and genera always italicized.

ICTV Nomenclature System

In addition to formal taxonomic systems, viruses are often informally categorized based on shared biological and physical characteristics. Common grouping criteria include host and tissue specificity, capsid shape, presence of unique genes or enzymes, and genome traits such as being naked or enveloped, single-stranded (ss) or double-stranded (ds) DNA or RNA, segmented or nonsegmented, and positive-strand (+) or negative-strand (-) RNA.

Informal Virus Classification

The Baltimore classification system is an alternative to the ICTV nomenclature that categorizes viruses into seven groups based on their genome characteristics (such as DNA or RNA, single- or double-stranded) and replication strategies. Viruses in each of these seven categories share common genetics and biology. The groups are:

1. Double-stranded DNA (dsDNA) viruses (e.g., Adenoviruses, Herpesviruses, Poxviruses)
2. Single-stranded DNA (ssDNA) viruses (e.g., Parvoviruses)
3. Double-stranded RNA (dsRNA) viruses (e.g., Reoviruses)
4. Positive-sense single-stranded RNA ((+)ssRNA) viruses (e.g., Coronaviruses, Picornaviruses, Togaviruses)
5. Negative-sense single-stranded RNA ((−)ssRNA) viruses (e.g., Orthomyxoviruses, Rhabdoviruses)
6. Single-stranded RNA reverse-transcribing (ssRNA-RT) viruses with a DNA intermediate (e.g., Retroviruses)
7. Double-stranded DNA reverse-transcribing (dsDNA-RT) viruses with an RNA intermediate (e.g., Hepadnaviruses)

Baltimore classification of viruses

The classification of viruses is based on several distinguishing characteristics, including their morphology, type of nucleic acid, host range, cell specificity, and specialized enzymes carried within the virion.

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