A study of this taxon suggests that this group of viruses had a marine origin - specifically the Southern Ocean - and that they have subsequently spread to both the Old and New World [REF].
There are three subgroups in this genus: the Semliki Forest virus subgroup (Semliki Forest, O'nyong-nyong and Ross River viruses); the eastern equine encephalitis virus subgroup (eastern equine encephalitis and Venezuelan equine encephalitis viruses) and the Sindbis virus subgroup [REF].