Virusarter

Virusarter, or virus species, is the basic unit of classification in virology. In the taxonomy maintained by the International Committee on Taxonomy of Viruses (ICTV), a virus species represents a replicating lineage that is genetically distinct and shares a defined set of properties. Viruses are obligate intracellular parasites; because they depend on host cells to reproduce, species boundaries are based on evolutionary relationships and combined genetic, structural, ecological, and antigenic characteristics rather than clinical symptoms alone.

The ICTV framework organizes viruses into realms, families, genera, and species. A virus species is the smallest unit that can be delineated by multiple properties; demarcation criteria include genome type and organization, sequence similarity, host range, tissue tropism, and antigenic relationships. Thresholds vary by virus group, reflecting different rates of evolution and data availability.

Virions exhibit a range of genomes: DNA or RNA, single- or double-stranded, segmented or nonsegmented. They may possess envelopes derived from host membranes and exhibit various capsid geometries, such as icosahedral or helical symmetry. Replication relies on the host cell's machinery, and different species employ diverse life cycles and gene repertoires.

Examples of well-known virus species include those associated with hepatitis C virus and influenza A virus, among many plant, animal, and bacterial viruses. New virus species are proposed when a lineage proves to be sufficiently distinct by multiple criteria and are reviewed by ICTV before acceptance.

Limitations: the species concept in virology is a practical framework rather than a strict biological boundary. Recombination, genome reassortment, and rapid mutation can blur boundaries, so classification emphasizes lineage coherence and consensus within the scientific community for surveillance and communication.