Recently, the International Committee on Taxonomy of Viruses has re-classified the two genotypes as two different species: PRRSV1 and PRRSV2.
Both PRRSV1 and PRRSV2 belong to the genus Porarterivirus, one of the five genera established within the family Arteriviridae, placed with the families Mesoniviridae, Roniviridae and Coronaviridae in the order Nidovirales.
Species in the family Arteriviridae have a nucleotide identity of around 40-70%. Although arteriviruses share an evolutionary relationship with other members of the order, several of their characteristics are unique:
- Genomic organization and size (from 12.7 to 15.7 kb).
- High genetic variability.
- Morphology of the virion.
- Limited cellular specificity (all replicate in alveolar macrophages, apart from WPDV and some viruses that affect simians, for which the cell types are yet unknown).
- Capacity to cause persistent or, in some cases, asymptomatic infections.