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A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
This is a list of all virus species, including satellites and viroids. Excluded are other ranks, and other non-cellular life such as prions. Also excluded are common names and obsolete names for viruses. The taxonomy is taken from ICTV taxonomy 2022 release. For a list of virus families and subfamilies, see List of virus families and subfamilies.
Illustration of a SARS-CoV-2virion. A virusis a tiny infectious agentthat reproducesinside the cellsof living hosts. When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new viruses assemble in the infected host cell.
Viral disease. A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. [1] Examples are the common cold, gastroenteritis and pneumonia. [2]
Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms . Viruses are classified by phenotypic characteristics, such as morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause.
Smallpox was an infectious disease caused by variola virus (often called smallpox virus), which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980, making smallpox the only human disease to have been eradicated to date.
Virology. Gamma phage, an example of virus particles (visualised by electron microscopy) Virology is the scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction ...
Measles is a highly contagious, vaccine-preventable infectious disease caused by measles virus. [3] [5] [11] [12] [13] Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. [7] [8] Initial symptoms typically include fever, often greater than 40 °C (104 °F), cough, runny nose, and inflamed eyes.