[A new virus: the human herpesvirus 6].

Human herpesvirus 6 (HHV-6) was discovered in 1986. This novel virus is genetically related to cytomegalovirus. HHV-6 mainly infects T lymphocytes but its tropism appears to be much wider and probably involves some epithelial cells. Two HHV-6 variants, designated as A and B, can be distinguished by genetical and immunological analysis. HHV-6 infection is ubiquitous and widespread; it occurs most often during infancy and it is life-long. During primary infection, HHV-6 is the causative agent of exanthem subitum and fever episodes without rash in infants. HHV-6 is suspected to be the causative agent of opportunistic infections such as pneumonitis and retinitis in immunocompromised subjects. Its role in human immunodeficiency virus infection, lymphomas and chronic fatigue syndrome is controversial. In vitro, HHV-6 is sensitive to ganciclovir and foscarnet.