Introduction

The virus order Mononegavirales was established in 1991 to accommodate related viruses with nonsegmented, linear, single-stranded, negative-sense RNA genomes distributed among three families [19, 20]. Today, the order includes 8 families [1, 2, 11, 21]. Amended/emended order descriptions were published in 1995 [5], 1997 [22], 2000 [23], 2005 [24], 2011 [6], 2016 [2], and 2017 [3]. In 2017, the Study Groups of the International Committee on Taxonomy of Viruses (ICTV) responsible for the taxonomy of the order and its 8 families assigned unclassified mononegaviruses to existing or novel taxa and continued efforts to streamline the order nomenclature in collaboration with other virus experts. Here we present the changes that were proposed via official ICTV taxonomic proposals (TaxoProps) at http://www.ictvonline.org/ in 2017 and accepted by the ICTV Executive Committee (EC). These changes are part of the official ICTV taxonomy as of 2018.

Taxonomic changes at the order rank

In 2018, no changes were made at the order rank.

Taxonomic changes at the family rank

Bornaviridae

The family Bornaviridae was expanded in 2018 by creation of a second genus (Carbovirus), including two novel species for the newly discovered jungle carpet python virus (JCPV) and southwest carpet python virus (SWCPV) found in carpet pythons (Pythonidae: Morelia spilota), respectively [10]. The previously established genus Bornavirus was renamed Orthobornavirus to remove the ambiguity of the terms “bornavirus”/“bornaviral” that resulted due to the creation of the second genus (in absence of the genus name change, “bornavirus”/“bornaviral” could refer either to all members of the family Bornaviridae or only to those of the genus Bornavirus). All binomial species names of the genus Bornavirus were adjusted by replacing the genus epithet “bornavirus” with “orthobornavirus” (TaxoProps 2017.005M.A.v1.Carbovirus and 2017.004M.A.v1.Bornaviridae_ren).

Filoviridae

The species name Taï Forest ebolavirus was changed to Tai Forest ebolavirus by removal of the diaeresis (TaxoProp 2017.001G.A.v2.43spren).

Mymonaviridae

In 2018, no changes were made at the family rank.

Nyamiviridae

In 2018, no changes were made at the family rank.

Paramyxoviridae

The genus Avulavirus was expanded in 2018 by the addition of six species (TaxoProp 2017.010M.A.v2.Avulavirus_6sp). The species Avian avulavirus 14–16 were established for avian paramyxoviruses 14–16 (APMV-14–16) that were recently discovered in an unspecified duck in Japan, a white-rumped sandpiper (Scolopacidae: Calidris fuscicollis) in Brazil, and unspecified birds in South Korea, respectively [12, 27, 28]. The species Avian avulavirus 17–19 were established for Antarctic penguin viruses A–C (APVA–APVC) that were recently discovered in Antarctic long-tailed gentoo penguins (Spheniscidae: Pygoscelis papua) [18].

Pneumoviridae

In 2018, no changes were made at the family rank.

Rhabdoviridae

The genus Ledantevirus was expanded in 2018 by one species, Kanywara ledantevirus, for Kanywara virus (KYAV) recently discovered in an unclassified nycteribiid batfly in Uganda [8] (TaxoProp 2017.009M.A.v1.Ledantevirus_sp).

The genus Lyssavirus was expanded by the addition of two novel species, Gannoruwa bat lyssavirus and Lleida bat lyssavirus, for Gannoruwa bat lyssavirus (GBLV) and Lleida bat virus (LLEBV), recently discovered in Indian flying foxes (Pteropus medius) in Sri Lanka and in a Schreibers’s long-fingered bat (Miniopterus schreibersii) in Spain in 2011, respectively [4, 9, 15] (TaxoProps 2017.013M.A.v1.Lyssavirus_sp and 2017.014M.A.v1.Lyssavirus_sp).

Finally, the genus Tibrovirus was expanded by one species, Beatrice Hill tibrovirus, for Beatrice Hill virus (BHV) discovered in 1984 in Australian biting midges (Ceratopogonidae: Culicoides peregrinus) [26, 29] (TaxoProp 2017.019M.U.v1.Tibrovirus_sp).

Sunviridae

In 2018, no changes were made at the family rank.

Outlook

The taxonomy of viruses of the order Mononegavirales remains in flux and additional important changes are likely forthcoming. Indeed, in 2017, two additional taxonomic proposals that would affect the order Mononegavirales were debated during the most recent ICTV EC meeting in Singapore. TaxoProp 2017.006M.U.v2.Negarnaviricota proposes

  • establishment of a phylum for negative-sense RNA viruses that is subdivided into two subphyla;

  • establishment of a sister order to the order Mononegavirales to accommodate the recently discovered “chǔviruses” [13, 25]; and

  • combination of both sister orders in a class assigned to one of the subphyla.

TaxoProp 2017.016M.U.v3.Mononegavirales_rev proposes

  • expansion of the family Mymonaviridae by 6 species for novel soybean leaf-associated viruses and an invertebrate virus [16, 17, 25];

  • transfer of the nyamiviral genus Peropuvirus into a new family and expansion of the genus by 6 species for novel invertebrate viruses [13, 25];

  • transfer of the free-floating genus Crustavirus into the family Nyamiviridae; the expansion of Crustavirus by two species for novel invertebrate viruses; and the expansion of Nyamiviridae by an additional three genera that include a total of five species for novel invertebrate viruses [13, 25];

  • establishment of a new family that absorbs the previously free-floating genus Anphevirus and expansion of this genus by six species for novel invertebrate viruses [7, 13, 14, 25]; and

  • dissolution of the previously free-floating genera Chengivirus and Wastrivirus and transfer of their species into the genus Arlivirus, expansion of Arlivirus by three new species for novel invertebrate viruses [13, 25], and transfer of this genus into a new family.

These two proposals failed to find unanimous approval at a final ICTV EC vote in fall of 2017 and were deferred to the 2018 ICTV EC meeting, at which a simple majority vote would suffice for approval of the original proposals.

Summary

A summary of the current, ICTV-accepted taxonomy of the order Mononegavirales is presented in Table 1.

Table 1 ICTV-accepted taxonomy of the order Mononegavirales as of 2018. Listed are all mononegaviruses that have been classified into species
Full size table