The viral order Mononegavirales was established in 1991 to accommodate related viruses with nonsegmented, linear, single-stranded negative-sense RNA genomes. These viruses were initially assigned to three mononegaviral families: Filoviridae, Paramyxoviridae, and Rhabdoviridae [20, 21]. In subsequent years, these families continued to grow through the inclusion of numerous novel species and genera, and the order was therefore emended in 1995 [4], 1997 [23], 2000 [24], 2005 [25], and 2011 [8]. The families Bornaviridae and Nyamiviridae joined the other three mononegaviral families in 1996 [22] and 2014 [1, 11], respectively. In 2015, the Study Groups of the International Committee on Taxonomy of Viruses (ICTV) responsible for the taxonomy of the order and its five families embarked on a joint effort to assign unclassified mononegaviruses to existing or novel taxa and to streamline order nomenclature. Here we present a brief overview of the first round of these efforts, which by now is accepted by the ICTV Executive Committee and, thereby, is official taxonomy.

Taxonomic changes at the order level

In recent years, several mononegaviruses have been described that are only distantly related to the members of the families Bornaviridae, Filoviridae, Nyamiviridae, Paramyxoviridae, and Rhabdoviridae. These viruses include Sclerotinia sclerotiorum negative-stranded RNA virus 1 (SsNSRV-1) found in an ascomycete in China [16]; Sunshine Coast virus (SunCV; previously called Sunshine virus) isolated from Australian carpet pythons [10]; and Líshí spider virus 2 (LsSV-2), Sānxiá water strider virus 4 (SxWSV-4), Tǎchéng tick virus 6 (TcTV-6), Wēnzhōu crab virus 1 (WzCV-1), and Xīnchéng mosquito virus (XcMV) detected in Chinese arthropods [15]. To accommodate these viruses in the order and to appropriately reflect their phylogenetic relationships to other mononegaviral taxa, two new families and four free-floating genera were established: Mymonaviridae (accommodating SsNSRV-1), Sunviridae (SunCV), Anphevirus (XcMV), Arlivirus (LsSV-2), Chengtivirus (TcTV-6), Crustavirus (WzCV-1), and Wastrivirus (SxWSV-4). In addition, the paramyxoviral subfamily Pneumovirinae was elevated to family status (Pneumoviridae) because the members of this taxon are as closely related to filoviruses as to the members of the paramyxoviral subfamily Paramxyovirinae (now dissolved) (Table 1).

Table 1 Taxonomy of the order Mononegavirales as of 2016

Taxonomic changes at the family level

The monogeneric family Bornaviridae was reorganized in 2015 by establishing five distinct species in the genus Bornavirus [2, 12] following a non-Latinized binomial species name format [29]. These efforts were continued in 2016 by expanding the genus by an additional two species (Elapid 1 bornavirus for Loveridge’s garter snake virus 1 [27] and Psittaciform 2 bornavirus for parrot bornavirus 5 [9, 18]) (Table 1).

The monogeneric family Nyamiviridae was expanded to include a second genus (Socyvirus) for the until-then free-floating nyamivirus species Soybean cyst nematode virus. This species name was changed to Soybean cyst nematode socyvirus to adhere to the non-Latinized binomial species name format [29] (Table 1).

The family Paramyxoviridae was emended by expanding the genus Avulavirus by three species (Avian paramyxovirus 10-12 for avian paramyxoviruses 10-12, respectively [5, 19, 28]), the genus Henipavirus by three species (Cedar henipavirus for Cedar virus [17], Ghanaian bat henipavirus for Kumasi virus [GH-M74a] [7], and Mojiang henipavirus for Mòjiāng virus [31]), the genus Morbillivirus by one species (Feline morbillivirus for feline morbillivirus [30]) and the genus Respirovirus by one species (Porcine parainfluenza virus 1 for porcine parainfluenza virus 1 [14]). The species Simian Virus 10 was dissolved on the evidence that simian virus 10 is an isolate of human parainfluenzavirus 3 rather than a distinct virus [13]. The genus Pneumovirus, now included in the new family Pneumoviridae, was renamed Orthopneumovirus to avoid confusion between family and genus members (Table 1).

The family Rhabdoviridae was expanded by two genera: Dichorhavirus (new; [6]) and Varicosavirus (previously free-floating outside of the order) to accommodate bisegmented plant viruses (coffee ringspot virus and orchid fleck virus; lettuce big-vein associated virus). The species Alfalfa dwarf cytorhabdovirus (for alfalfa dwarf virus [3]) was added to the genus Cytorhabdovirus. Finally, the non-Latinized binomial species name format [29] was applied throughout the family (Table 1).

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