Gammaherpesvirinae is a subfamily of viruses in the order Herpesvirales, in the family Herpesviridae. Viruses in Gammaherpesvirinae are distinguished by reproducing at a more variable rate than other subfamilies of Herpesviridae. Mammals serve as natural hosts. There are currently 32 species in this subfamily, divided among 4 genera. Diseases associated with this subfamily include: HHV-4: infectious mononucleosis. HHV-8: kaposi's sarcoma. Herpesviruses represent a group of double-stranded DNA viruses distributed widely within the animal kingdom. The family Herpesviridae, which contains eight viruses that infect humans, is the most extensively studied group within this order and comprises three subfamilies, namely Alphaherpesvirinae, Betaherpesvirinae and Gammaherpesvirinae. Gammaherpesviruses belong to four separate genera: the well-established genera Lymphocryptovirus and Rhadinovirus and the more recently defined genera Macavirus and Percavirus. Gammaherpesviruses are of primary interest due to the two human viruses, EBV and KSHV and the diseases they cause.The gammaherpesviruses replicate and persist in lymphoid cells but some are capable of undergoing lytic replication in epithelial or fibroblast cells. Gammaherpesviruses may be a cause of chronic fibrotic lung diseases in humans and in animals.