The genus Nyavirus includes three species. Based on the genomic structure and phylogeny, Sierra Nevada virus (SNVV), Nyamanini virus (NYMV), and Midway virus (MIDWV) are closely related (Mihindukulasuriya et al., 2009, Rogers et al., 2014). Based on PASC analysis, the SNVV genomic sequence is about 50% identical to NYMV and MIDWV genomes, whereas the identity between NYMV and MIDWV is closer (≈63%).
Virions are enveloped and spherical with a diameter of 100–130 nm (Figure 1.Nyamiviridae).
Non-segmented, negative-sense RNA.
Nyavirus genomes encode six structural proteins. Among them, the nucleocapsid protein (N), glycoprotein (G), and RNA-directed RNA polymerase (L) protein are identified on the basis of sequence similarity and structural properties shared with mononegavirus homologues. The functions of the other encoded proteins are largely unknown, but may be those of matrix and polymerase cofactor proteins (Mihindukulasuriya et al., 2009).
Genome organization and replication
Nyavirus negative-sense RNA genomes range from 11.6–11.8 kb (Figure 2.Nyamiviridae). Nyaviruses have non-segmented genomes with six ORFs that encode the structural proteins (Mihindukulasuriya et al., 2009, Rogers et al., 2014). Knowledge of nyavirus replication is limited. Nyamanini virus replicates in the nucleus of infected cells (Herrel et al., 2012).
Although NYMV and MIDWV have been isolated from birds of different species and their ticks, it is unclear whether SNVV can also infect birds.
Derivation of names
Nyavirus: from Nyamanini Pan” (place of isolation of Nyamanini virus in South Africa) and virus (ending denoting a virus genus); Neo-Lat. n. neut. sg. Nyavirus – the genus of nyaviruses. Species: named after the location where species members were first identified.
Species demarcation criteria
The SNVV genome is about 50% similar to those of NYMV and MIDWV genomes, whereas the nucleotide sequence identity between NYMV and MIDWV is closer (≈63%).
|Species||Virus name||Isolate||Accession number||RefSeq number||Available sequence||Virus Abbrev.|
|Midway nyavirus||Midway virus||RML47153||FJ554525||NC_012702||Complete genome||MIDWV|
|Nyamanini nyavirus||Nyamanini virus||tick 39||FJ554526||NC_012703||Complete genome||NYMV|
|Sierra Nevada nyavirus||Sierra Nevada virus||KF530058||NC_024376||Complete genome||SNVV|
Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.
Related, unclassified viruses
San Jacinto virus