Editing Virus classification (section)

===Structure-based virus classification===
{{see also|List of higher virus taxa}}
It has been suggested that similarity in virion assembly and structure observed for certain viral groups infecting hosts from different domains of life (e.g., bacterial tectiviruses and eukaryotic adenoviruses or prokaryotic Caudovirales and eukaryotic herpesviruses) reflects an evolutionary relationship between these viruses.<ref>{{cite journal | vauthors = Bamford DH | title = Do viruses form lineages across different domains of life? | journal = Research in Microbiology | volume = 154 | issue = 4 | pages = 231–6 | date = May 2003 | pmid = 12798226 | doi = 10.1016/S0923-2508(03)00065-2 | doi-access = free }}</ref> Therefore, structural relationship between viruses has been suggested to be used as a basis for defining higher-level taxa – structure-based viral lineages – that could complement the ICTV classification scheme of 2010.<ref>{{cite journal | vauthors = Krupovič M, Bamford DH | title = Order to the viral universe | journal = Journal of Virology | volume = 84 | issue = 24 | pages = 12476–9 | date = December 2010 | pmid = 20926569 | pmc = 3004316 | doi = 10.1128/JVI.01489-10 }}</ref>

The ICTV has gradually added many higher-level taxa using relationships in protein folds. All four realms defined in the 2019 release are defined by the presence of a protein of a certain structural family.<ref>{{cite web|url=https://ictv.global/taxonomy|title=Virus Taxonomy: 2019 Release|date=|website=talk.ictvonline.org|publisher=International Committee on Taxonomy of Viruses|access-date=26 April 2020|quote=}}</ref>