A PRACTITIONERS GUIDE TO HUMAN HERPESVIRUS-6 (HHV-6) AND HUMAN HERPESVIRUS-7 (HHV-7)

Human herpesvirus-6 (HHV-6) and HHV-7 are newly recognized ubiquitous human viruses first discovered in patients with AIDS or lymphoprolifer ative disorders. Much more information is available about the clinical characteristics of infection with HHV-6 than HHV-7. Primary infection with HHV-6 occurs in early childhood and is most commonly manifested as an undifferentiated highly febrile illness, with seizures noted to be the most common complication. A subset of children develop the clas sic manifestations of roseola infantum or exanthem subitum. Other neur ologic diseases in adults such as encephalitis and multiple sclerosis also have been linked to HHV-6; however, the role of HHV-6 in these cl inical entities has not been fully elucidated. Although HHV-6 and HIV are both tropic for CD4(+) lymphocytes and interact in vitro, there is no evidence at present that HHV-6 plays a role in HIV disease. HHV-7 is similar to HHV-6 in genetic organization and structure. Little is k nown of the clinical characteristics of infection with HHV-7 or its ab ility to cause disease in children or reactivation in adults.