HUMAN HERPESVIRUS-7 - ANOTHER CAUSAL AGENT FOR ROSEOLA (EXANTHEM-SUBITUM)

Human herpesvirus 7 (HHV-7) was isolated from peripheral blood mononuc lear cells of two infants with typical exanthem subitum. The HindIII-, BamHI-, and EcoRI-digested DNA patterns of the isolated viruses were very similar to that of the prototype HHV-7 (RK strain), but different from that of human herpesvirus 6 (HHV-6). During the convalescent per iod of the first patient, the titer of antibody to HHV-7 rose from <1: 10 to 1:320 by an immunofluorescence antibody test, whereas the titer of antibody to HHV-6 remained <1:10. In the second patient, who had tw o independent episodes of exanthem subitum during 2 months, both HHV-6 and HHV-7 were sequentially isolated; seroconversion to HHV-6 occurre d during the first episode and to HHV-7 during the second episode. In addition, sera from another 15 children who had episodes of exanthem s ubitum were serologically tested for antibodies to HHV-6 and HHV-7 by immunofluorescence antibody test. Five of seven patients had seroconve rsion to HHV-7 just after having typical signs and symptoms of exanthe m subitum. These results suggest that HHV-7 is one of the causative ag ents of exanthem subitum.