Virus community views on the possible extension of virus taxonomic assignments to a below-species rank.

Abstract

The International Committee on Taxonomy of Viruses (ICTV) is considering a proposal submitted in July 2025 to create an optional additional taxonomic rank below the level of species. This was designed to increase the precision of taxonomic assignment where clinical or other regulatory distinctions need to be made between viruses assigned to the same species. To understand current classification practice and to gauge opinion on the proposal to formalize a below-species taxon, current ICTV study group members (n=746) representing over 100 Study Groups were invited to complete a survey, from whom 240 completed forms and comments were collected in November 2025. The survey also recorded opinions on the use of designators, such as 'type', 'isolate' and 'subspecies' for below-species assignments and the typographic format of their names, for example, whether to be italicized and/or Latinized.Overall, a 6 : 1 majority favoured the introduction of an optional below-species taxonomic rank managed by the ICTV, and was particularly supported by those working in animal and veterinary virology fields where various forms of community-supported below-species classifications are used. There was also support to formalize and taxonomically assign existing classifications of viruses and define their nomenclature. Names might be formatted using the Latin alphabet but with less support for italicization or for Latinization of the below-species epithet. The survey data and associated comments will be considered in further discussions at the next ICTV Executive Committee meeting in November 2026. We thank all of their survey respondents for their invaluable and expert contributions to this consultative process.