The basis of arbovirus classification.

The biologically defined set of arboviruses contains well over 300 separate viruses which have been subdivided into some 40 serological groups on the basis of antigenic cross-reactivity. More than three quarters of all arboviruses can now bw placed into one of the following five major taxonomic genera based upon the fundamental properties of the virion: alphavirus, flavivirus, orbivirus, rhadovirus, bunyavirus. There are 20 alphaviruses, representing serological Group A, and 57 flaviviruses in serological Group B; these two genera fall into the familty Togaviridae. The 40 orbiviruses, in the family Reoviridae, include some 8 serological groups, and the 8 rhabdoviruses, in the family Rhabdoviridae include another 3 groups. About 160 bunyaviruses, family Bunyaviridae, are divisible into 20 serological groups, 10 of which show intra-group cross-reactions in the Bunyamwera supergroup. One arbovirus contains DNA, namely African swine fever virus; this is classified as an Iridovirus, or icosahedral cytoplasmic deoxyvirus. Nodamura virus, which has been classified as a picornavirus, must be reclassified on the evidence that it possesses a divided genome. A number of arboviruses remain unclassified in taxonomic terms. The absence of arbovirus representatives in several major genera, such as the adenoviruses and the myxoviruses is of no interest.