Virology

- Virology

Virology is the scientific discipline that studies the biology of viruses and viral diseases, including their distribution, biochemistry, physiology, molecular biology, ecology, evolution and clinical aspects. 

Virology is the scientific study of living viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, the methods by which they infect and exploit host cells for reproduction, their interactions with host organism physiology and immunity, the Diseases, techniques for isolating and culturing them, and their use in research and therapy.

- Viral Diseases

A major motivation for studying viruses is because they cause many infectious diseases of plants and animals. The study of how viruses cause disease is viral pathogenesis. The degree to which a virus is pathogenic is its virulence. These fields of study are known as plant virology, animal virology, and human or medical virology.

- Detecting Viruses

There are several methods for detecting viruses, including detection of viral particles (virions) or their antigens or nucleic acids, and infectivity assays.

• Electron microscopy
• Growth in cultures
• Serology
• Polymerase chain reaction (PCR) and other nucleic acid detection methods
• Diagnostic tests

- Molecular Biology and Viruses

Molecular virology is the study of viruses at the nucleic acid and protein levels. Methods developed by molecular biologists have all proven useful in virology. Their small size and relatively simple structure make viruses ideal candidates for study by these techniques.

- Genetics and Viruses

- Virus Classification

A major branch of virology is virus classification. It is artificial because it is not based on evolutionary phylogeny, but on shared or distinguishing properties of viruses. It attempts to describe the diversity of viruses by naming and grouping them according to similarity. 

In 1962, André Lwoff, Robert Horne, and Paul Tournier were the first to develop a method of classifying viruses based on the Linnaeus classification system. The system is based on the classification of phylum, class, order, family, genus and species. 

Viruses are grouped according to their common properties (rather than those of their hosts) and the type of nucleic acid that forms their genome. In 1966, the International Committee on Taxonomy of Viruses (ICTV) was formed. The system proposed by Lwoff, Horne, and Tournier was not initially accepted by ICTV because the viruses' small genome size and high rate of mutation made it difficult to determine their ancestry out of order. Therefore, the Baltimore classification system has been used to supplement the more traditional hierarchy.  

Beginning in 2018, ICTV began to acknowledge deeper evolutionary relationships between viruses discovered over time and adopted a 15-level classification system from domain to species. In addition, some species within the same genus are grouped into one genome.