Human betaherpesvirus 7 (HHV-7) is one of nine known members of the Herpesviridae family that infects humans. HHV-7 is a member of Betaherpesvirinae, a subfamily of the Herpesviridae that also includes HHV-6 and Cytomegalovirus (HHV-5 or HCMV). HHV-7 often acts together with HHV-6, and the viruses together are sometimes referred to by their genus, Roseolovirus. HHV-7 was first isolated in 1990 from CD4+ T cells taken from peripheral blood lymphocytes. Signs and symptoms Both HHV-6B and HHV-7, as well as other viruses, can cause a skin condition in infants known as exanthema subitum, although HHV-7 causes the disease less frequently than HHV-6B. HHV-7 infection also leads to or is associated with a number of other symptoms, including acute febrile respiratory disease, fever, rash, vomiting, diarrhea, low lymphocyte counts, and febrile seizures, though most often no symptoms present at all. There are indications that HHV-7 can contribute to the development of drug-induced hypersensitivity syndrome (DIHS), encephalopathy, hemiconvulsion-hemiplegia-epilepsy syndrome, hepatitis infection, postinfectious myeloradiculoneuropathy, pityriasis rosea, and the reactivation of HHV-4, leading to "mononucleosis-like illness". Drug reaction with eosinophilia and systemic symptoms (DRESS) is a specific type of DIHS that may be linked to HHV-7 as the condition may develop in response to herpesvirus antigens. In one study, 76% of the 40 examined patients with DRESS exhibited some reactivation of Epstein-Barr virus, HHV-6, or HHV-7. Additionally, HHV-7 is currently suspected as a causative agent of lichen planus. In one dermatologic study, 33 skin biopsies were performed and HHV-7 was found at higher rates in lichen planus lesions. Remission of lichen planus was also associated with lower levels of HHV-7. HHV-7 was also detected in 79.3% of cervical tissue examined, indicating that sexual contact may be a route of transmission for HHV-7. Notably, HHV-7 and HHV-6 were detected in 56.3% of unspecified encephalopathy cases examined, with more HHV-7 positive cells in the gray matter of the frontal and temporal lobes HHV-7 is typically present in astrocytes and oligodendrocytes in the cerebral cortex, deep nuclei, and cerebellum. HHV-7 infection, along with HSV1, VZV, and HHV6, was associated with increased risk of dementia. However, further research is needed further elucidate the causative and correlative factors between HHV-7 and encephalopathy. Complications with HHV-7 infection has been shown to be a factor in a great variety of transplant types. Specifically, HHV-7 infection has been linked to a reactivation of cytomegalovirus (CMV) infection in renal transplant patients and may