HHV-6 là thứ sáu trong tám mô tả con người herpesviruses. Giống như các thành viên khác của nhóm, nó có một lõi điện tử dày đặc bao gồm DNA doublestranded (dài 160-170 kbp) bao quanh bởi các nucleocapsid trong hình dạng của một icosahedron. Vỏ bao quanh lớp vỏ, và trilaminar một màng bao quanh toàn bộ cấu trúc. | itself HHV-6-induced reactivation of other infectious agents such as CMV or some other event for which HHV-6 reactivation is merely a marker is responsible for the observed disease manifestations. Fever bone marrow suppression hepatitis pneumonitis encephalitis graft or organ rejection and an increase in infections from CMV and fungi have been associated with HHV-6. THE VIRUS HHV-6 is the sixth of eight described human herpesviruses. Like the other members of the group it has an electron-dense core composed of doublestranded DNA 160-170 kbp long surrounded by nucleocapsid in the shape of an icosahedron. A tegument surrounds the capsid and a trilaminar membrane surrounds the entire structure. The nucleocapsid is 90-110 nm in diameter and the mature virion ranges from 160 to 200 nm in diameter. The genome of HHV-6 is most closely related to HHV-7 of all other herpesviruses these two similar viruses are most closely related to CMV. Two variants of the virus have been described HHV-6A and HHV-6B. Although both utilize the ubiquitous human CD46 as a receptor there are likely to be other factors involved in attachment or fusion as the two variants display different cellular tropisms in tissue culture and in the host. These tropisms may relate to observed disease associations. HHV-6B causes nearly all HHV-6-associated roseola and has been implicated in most of the observed complications in immunosupressed hosts while HHV-6A has only rarely been implicated in disease. HHV-6B grows well in mature lymphocytes while HHV-6A replicates better in immature lymphocytes. EPIDEMIOLOGY HHV-6 is a ubiquitous virus which is found worldwide and appears to infect most children by the age of two years. The virus can be found in the saliva of around 70 of asymptomatic adults closely matching the seroprevalence in the adult population. Transmission is thought to occur by direct contact with infectious secretions passing from asymptomatic adults to seronegative children typically from mother
