Taxonomy
HHV-6A and HHV-6B were recognized by the International Committee on Taxonomy of Viruses (ICTV) as distinct species in 2012. Human Roseoloviruses include HHV-6A, HHV-6B and HHV-7.
Herpesvirus was established as a genus in 1971 in the first report of the ICTV. This genus consisted of 23 viruses among 4 groups. In 1976, a second ICTV report was released in which this genus was elevated to the family level - the herpetoviridae. Because of possible confusion with viruses derived from reptiles, the family name was changed in the third report (1979) to herpesviridae. In this report, the family Herpesviridae was divided into 3 subfamilies (alphaherpesvirinae, betaherpesvirinae and gammaherpesvirinae) and 5 unnamed genera; 21 viruses were recognized as members of the family.
In 2009, the order Herpesviridae was created. This was necessitated by the discovery that the herpes viruses of fish and molluscs are only distantly related to those of birds and mammals. Order Herpesvirales contains three families, the Herpesviridae, which contains the long-recognized herpesviruses of mammals, birds, and reptiles, plus two new families - the family Alloherpesviridae which incorporates herpesviruses of bony fish and frogs, and the family Malacoherpesviridae which contains viruses of molluscs.
As of 2012, this order currently has 3 families, 4 subfamilies (1 unassigned), 18 genera (4 unassigned) and 97 species.
Read more about this topic: Human Herpesvirus 6