[Human herpesviruses 6 and 7].

By new methods for propagating cells of the immune system and for detecting infectious agents in disease tissue, 4 human herpesviruses have been discovered during the past decade: human herpesvirus 6 variants A and B (HHV-6A and HHV-6B), human herpesvirus 7 (HHV-7), and human herpesvirus 8 (HHV-8). Only HHV-8 has been linked to a disease that might be described as new, that is AIDS-associated Kaposi's sarcoma. No disease has been clearly linked to HHV-6A infection, HHV-6B is the major etiologic agent of exanthem subitum, and HHV-7 infection is associated with febrile exanthem which mimics exanthem subitum cases and occurs somewhat later than primary HHV-6B infection. Over 90% of the population has been infected with either or both HHV-6A and HHV-6B and over 85% with HHV-7. Both history and biology suggest that these viruses have a broad clinical spectrum and that they are each linked with significant and specific clinical entities. The clinical, epidemiological, and viral information has been obtained by new technologies such as virus isolation method, antigen and antibody assays, and molecular virology techniques including polymerase chain reaction amplification and in situ hybridization. However, since the viruses are ubiquitous, special attention will be required for evaluating an association between the results and disease condition.