Recent changes to virus taxonomy ratified by the International Committee on Taxonomy of Viruses (2022)

Abstract

This article reports the changes to virus taxonomy approved and ratified by the International Committee on Taxonomy of Viruses (ICTV) in March 2022. The entire ICTV was invited to vote on 174 taxonomic proposals approved by the ICTV Executive Committee at its annual meeting in July 2021. All proposals were ratified by an absolute majority of the ICTV members. Of note, the Study Groups have started to implement the new rule for uniform virus species naming that became effective in 2021 and mandates the binomial ‘Genus_name species_epithet’ format with or without Latinization. As a result of this ratification, the names of 6,481 virus species (more than 60 percent of all species names currently recognized by ICTV) now follow this format.

Introduction

Changes to virus taxonomy (the universal scheme of virus classification of the International Committee on Taxonomy of Viruses [ICTV]) take place annually and are the result of a multi-stage process. In accordance with the ICTV Statutes (https://ictv.global/statutes), taxonomic proposals (TaxoProps) submitted to the ICTV Executive Committee (EC) undergo a review process that involves input from the ICTV Study Groups (SGs) and Subcommittees (SCs), other interested virologists, and the EC. After final approval by the EC, proposals are presented for ratification to the full ICTV membership by posting on the ICTV website (https://ictv.global/) followed by an electronic vote.

The latest set of proposals approved by the EC was made available on the ICTV website in early 2022 (see https://ictv.global/proposal/MSL37/ for all proposals combined into a single zip file, and use the links provided in the References to this publication to access individual proposals). A list of proposals was then emailed on 6^th February 2022 to the 184 members of ICTV, namely the EC Members, Life Members, ICTV SC Members including the SG chairs and the Bioinformatics Expert Group members, and ICTV National Representatives. Members were then requested to vote on whether to ratify the taxonomic proposals. Voting closed on 11^th March 2022.

Changes to virus taxonomy ratified in 2022

All 174 proposals were ratified by ICTV members, in every case receiving an absolute majority of votes; at least 68% of eligible voters approved each proposal. A summary of the taxonomy changes enacted by ratification of the proposals is provided in Table 1; there were no proposals to change ICTV Code or ICTV Statutes this year. Each proposal is cited and listed in the References to acknowledge the authors’ efforts and to provide links to the specific proposal on the ICTV website [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175]. These documents remain available for those who wish to see the full details of the proposals. TaxoProp 2020.002G, ratified in 2021 [175], specified a procedure for expedited correction of unintended errors that may occur during proposal writing but clearly do not reflect the intention of the proposers, as described in the submitted proposal documentation. Examples of such errors include assignment of a lower-rank taxon to an incorrect higher rank, inadvertent introduction of duplicate taxon names, or assignment of a misspelled taxon name. Since the changes ratified by ICTV take effect immediately, this mechanism was used to correct several proposals in the current cycle. The corrections are listed in proposals 2021.097B [101], 2021.014M [129], 2021.042M [150] and 2021.043M [151].

Table 1 Summary of taxonomic changes approved in March 2022

Another important change ratified in 2021 was the adoption of a uniform binomial format for naming of virus species [176]. The ICTV SGs have been charged with conversion of all existing virus species names to the new binomial format, and two groups of authors affiliated with ICTV have recently provided guidance on designing and writing virus species' names [177]. With the ratification described here, 6,481 virus species out of 10,434 in the ICTV official Master Species List (MSL) adhere to the required binary format. The process of name conversion continues and is expected to be completed by the EC meeting planned for 2023. This system concerns only the names of virus species and does not affect the names of viruses [177].

Also of note, one proposal [107] established the family Polydnaviriformidae, the first high-order taxon comprising viriforms, the classifiable entities that were explicitly included in the ICTV remit in 2021. The list of all new orders and new families ratified in 2022 is provided in Table 2.

Table 2 New orders and families ratified by ICTV in 2022

Conclusion

All proposals submitted for ratification were ratified by an absolute majority of the ICTV, and the changes are now part of official ICTV taxonomy. An up-to-date list of all approved taxa, which now includes 10,434 virus species, can be found on the ICTV website: see https://ictv.global/msl/ for the MSL and https://ictv.global/vmr/ for the Virus Metadata Resource (VMR) that provides an exemplar virus isolate for each species along with the GenBank accession number of the isolate.